Note: My viewpoint is roughly the same as Madara's, so if you want the tl;dr read his post. I've tried to expand on where exactly the boundaries should be in my view.
I think this is a matter of two different viewpoints. If you think this site should focus on anime and manga as artistic media, then you probably don't think we should expand.
I tend to see anime and manga more as a culture, at least in the West. There are lots of games, manga-style comics (including manhwa and manhua), and anime-style cartoons which are targeted at, and are just as popular as, the average anime/manga series, and it's strange to not be able to discuss them here. That isn't to say that we're expanding our scope to include Star Trek, even though Star Trek probably is popular among manga fans. But we're including things that would be natural to discuss on an anime-themed site. What exactly those are is up for debate.
The following are my proposed expansions of the scope. I've tried to simultaneously be open about what sorts of topics we allow but set fairly strict boundaries.
Manhwa and Manhua, being commonly based off of Japanese Manga, are obvious choices. There really wasn't ever any reason to ban them except that it was convenient to define Manga by the origin. But that convenience for us isn't worth excluding a number of good questions about these series.
OEL manga is also in this category, but differentiating it from comic books/graphic novels can be difficult. I propose the following test: If a regular manga reader who is not familiar with the series can immediately tell that it is not manga from one or two pages (ignoring things like page orientation) then it should be allowed. This would include things like Megatokyo but not Homestuck. Most OEL manga identify themselves as such, and they tend to be published by only a few companies, so there are unlikely to be very many borderline cases. I also don't think we'll get a lot of questions on this topic, so putting too much thought into where the borders are seems like a waste of time at this point.
Some questions related to Manhwa and Manhua, whose statuses might be under consideration given this change:
Likewise, including cartoons based on anime, where the primary fanbase is highly correlated with the anime fanbase, seems okay. That will have to be judged on a case-by-case basis. avatar-the-last-airbender was deemed to be okay, but Samurai Jack was not, even though both are anime-inspired. There probably aren't too many shows that are in the grey area between these two, so this hopefully won't be a recurring problem.
I'd say that the test for borderline cases her is the following: if a relatively well-informed anime fan who has never seen or heard of this particular show could immediately discern that the show is probably not a Japanese anime, then it doesn't pass. If they can't tell just based off the artwork, it's probably anime-inspired enough that we can allow it. I think there aren't very many series that will pass that test (I could not think of any other than Avatar off the top of my head).
The following questions are related to avatar-the-last-airbender and are affected by this. As of now that is the only anime-style television show that is not anime but is being allowed.
It's worth noting that Scifi has a lot of Avatar-related questions (I count 53, which is more than all of their anime questions combined). It is one of the series that they are well-equipped to answer about. Whether or not we decide that can ask your Avatar question here, you can certainly do so there. This overlap is fine, as our communities have different cultures and interests, so you'll probably receive a different answer here or there. You should factor that in when you decide which site to ask on, and don't ask on both sites.
Live action adaptations of anime/manga, whether Japanese, Korean, Chinese, or from any other country, shouldn't be terribly controversial. At the moment, I do not believe we should expand beyond that to include all J-dramas, K-dramas, etc. While there are a lot of fans of these, the only cases where there's a large overlap between anime and drama fans are adaptations of anime/manga. I don't think this is really expanding our scope, but clarifying it.
At the moment I don't think we've had any questions about live-action versions specifically.
Games are a particularly tricky area. There are a lot of games which probably count as anime-style or anime-based. First, we definitely don't want to allow gameplay questions about these games. We aren't a gamer community, and we shouldn't strive to promote that content. If you want to ask gameplay questions, Arqade is a great site for a large number of games.
So we're left with questions about the story, characters, lore, etc. That's essentially the same as what we allow questions about in terms of anime. We also need to know how to define what "anime-style" or "anime-based" means. However, it's typically pretty clear whether a game counts as anime-style or not. Touhou Project games obviously count, and Grand Theft Auto games obviously don't. But there are a lot of intermediate cases.
I propose the following, though I'll admit I'm not happy about it. If the art style of the game is similar enough to anime-style that a fairly standard-looking anime could be made from it without changing the style, then it should be allowed. This excludes games with realistic art styles like Mass Effect, and also games with cartoon styles like PaRappa the Rapper, even though both of them have related anime series which are on-topic here.
If that's confusing, it's easier to show examples of what would be allowed. Pokemon, BlazBlue, The Tales RPGs, Arcana Heart, THE iDOLM@STER, and any games directly based on an anime are allowed. For reference, Mario, Halo, and Minecraft definitely don't fit the bill. I also suggest that we be fairly strict when it comes to new game series. If a series isn't obviously acceptable, then we shouldn't allow it without discussing it specifically on meta. This is mostly to prevent our site from getting flooded.
I view this policy as an extension of our policy allowing story questions about visual novels with some gameplay elements. We're now reducing the requirement from that the game is part-visual novel to that it's an anime-style game, which I think is fixing what was an inconsistency.
Some questions which are related and could potentially be affected by changes:
It's worth noting that plot-related questions are allowed at Arqade, though they are uncommon. As such this material would be on-topic on both sites. Our site has different culture and standards from Arqade, so the overlap isn't a problem, but you should consider which site to ask your question on and don't ask on both sites.
I'd also like to clarify that I do not think we should allow questions about the production of any of the above categories. anime-production is fine, because it's of direct interest to a sizable number of people in our community. However, asking about the production of a video game or a cartoon series really isn't on topic. Game Development, Graphic Design, and Movies & TV are all great sites in the SE network which will take some of those questions, but you should check their FAQs before asking.