According to Modojo, the PSP release of Advent Children will come before the DVD release. While I find this disheartening, it was a move I expected. They had to find a way to convince folks to buy the PSP version somehow. I for one won't succumb to this marketing ploy and will just wait for the DVD.
On the bright side, however, that things are still being spoken of in purely UMD and DVD terms perhaps means that there's not going to be a theatrical release. For me, that's a good thing, as I want to pay for the thing once, then watch it as much as I want and rewind at my own leisure, not wait another six months to be able to after paying $7 to go see it one time.
Also something worthy of note is that -- according to Square Net -- Square-Enix has two conferences slated for this month, one on April 13 and another on April 15. Hopefully some official release dates will finally come forth (and stay set in stone this time).