Next PT album will most likely not be out until late 2013, or early 2014.
As it looks right now, Steven Wilson has several things "higher" on his list:
*Solo-album #3 (writing, recording, mixing etc)
*Live in Mexico BluRay/DVD (mixing)
*Touring for solo-album #3
*Porcupine Tree Live (I'm not sure how much he will be involved since it's recorded already, but seeing as he wants control of things, I assume he will be mixing it)
*Blackfield 4 (he has taken a step down from the band, he has already recorded vocals for the album, but it still feels likely that he will mix the album)
*No-Man (this has only been rumoured really, but they haven't released anything since 2008, and Tim Bowness has sounded eager to do something with SW soon again)
*Other mixing jobs (He has done mixes for King Crimson and a few other classic Prog-bands, it feels logical that we'll see at least one or two more of those this year)
As much as I love PT, I feel like GfD is Steven Wilson's best album so far in his career, and if he keeps putting out albums of the same quality under his solo name, then I probably wont miss PT as much.