Nope, because he has other engagements.
But Marr did work on 10 tracks of the PSB's last album, and if they DO launch a full scale tour for their next album, don't be surprised if he tours with them since he said himself, by answering my own question through his website a year and a half ago, that he thought the Nightlife songs would have sounded much better if he had been on stage with them to play guitar.
Besides, he co-wrote a song on their 1996 Bilingual album, and played guitar on a couple of tracks on their Behaviour album I think. Also, he re-worked the song "I Want To Wake Up" in 1993 and, of course, worked with the PSB in Electronic. So they have a fairly long common history. Johnny Marr is, in a way, the third Pet Shop Boy.
Seb.