It won't happen, unfortunately. And if it did, I'd be very surprised. Tales of Phantasia isn't a small game (for when it was made) but that only got a 4 ep OAV as well.
Personally I'm expecting much the same as the ToP OAV. Some dramatic scenes in the first episode, followed by a jump to near the end where the gang visit Heimdall and are preparing to head to the final encounter. So basically a fanservice trip for us fans but nothing really substantial.
Either way, I'm looking forward to seeing the gang animated and can't wait to see which summons/abilities/spells etc. they'll decide to incorporate into it.
/Radiosity wants to see Genis casting Indignation or even Indignant Judgement at least once.
