If they're doing it now, to cash in on 'Hunger Games' watch them age up the majority of the cast to take advantage of the YA market. (Oh, yeah, and so 'little kids in battle' doesn't seem so squicky) Also, if the trailers/ads show children, people who haven't read the books (ie most people) will think it's a 'kid's movie'.
I dunno. I think Ender's Game would sell regardless of The Hunger Games. Whether or not they're cashing in, I don't think it would effect their sales. They're completely different ideas and Ender's Game has had time to get a devoted older following who's been waiting for this movie for decades. If they pull this off well, they could be looking at the success of LoTR, rather than Eragon.
The only thing they have in common in that they feature kids fighting each other. One has a military/sci-fi feel with pretend games and aliens. The other is about a death match in an arena with a teen girl lead. And, looking at the cast, unlike the Hunger Games, they've picked actors who're actually around the age of the characters. And they've got Harrison Ford, who's already seen success in sci-fi/action movies.
It'd be pretty much impossible to advertise the movie without showing kids in the ads. It's also kind of a kids movie. I mean, I read the book when I was nine/ten. It's taught in middle school and it's categorized as YA by most libraries.
As for merging Game and Shadow, I don't know if that could be done. I found Bean's story more fascinating, but merging that with Ender's would be difficult. Bean's has a lot more backstory and sub-plots that would detract from Ender's, and leaving any of it out would just make the story really confusing for anyone who hasn't read the book. It'd end up like the Harry Potter movies after #4. And since Bean doesn't go evil, I don't really see the point in showing an alternate view point to battle school.
An anime production would be fun, but I don't know, I have confidence in this project. If they pull it off like the effects in The Matrix, or AI, or Minority Report, or The Chronicles or Riddick, or even Alien Resurrection, it could be pretty badass. Minimizing the battleroom sequences, which, tbh, I thought were pretty boring in the book, could work too. The only battles they really need to show are the training sequences with Alai and Petra, the battle that Ender disobeys Bonzo in, the battle with Rat Army, and one or two Dragon Army battles. I just hope they eliminate the naked little boys.