Wow that's odd, I wonder why they're doing this for a last gen RPG <_<
You could ask the production company the same thing. The anime began airing in Japan in October 2008, with the "next-gen" systems being two years in and Abyss being nearly three years old. And Symphonia came out in 2003 in Japan and they're still working on the anime adaptation for that. Abyss was particularly sucessful and especially popular among the fanbase, that's probably why they animated it.
Well, regardless, they might have some trouble getting Tara Strong onboard if the ToS OVA someday makes it over. I seem to have this vague recollection that she isn't a fan of dubbing things that have already been animated. She's only got a couple of anime credits, but quite a decent list of video game and American cartoon credits.
While Strong is an excellent actress, I didn't mind Dawn of the New World's Presea. She seems to have tricked a lot of people into believing that she's the original actress (despite Strong doing SAG-only work)!
I'm more worried about Strong and Menville myself. I don't think Shiloh has done any traditional anime work, while his horrid replacement was in Gurren Lagann, among other titles. People say Menville hates anime, but then again, people said he didn't want to voice Lloyd ever again, but that directly contradicts what the man himself told me.
Oh well. Bandai knows how to please me, they just licensed K-On! and now Abyss is coming.