Duh, The Astonishing is his next solo album, he wrote basically the whole thing
It isn't. He didn't.
The story is his, yes, but the music he mainly co-wrote it with Rudess. Also, it's a DT album, in which although Myung, LaBrie and Mangini don't have any formal 'writing credits' it's a band effort in which everyone put a piece of themselves in it.
That dynamic is complex enough to discard it as a JP 'solo' album.
And now, within the subject matter, I for one cannot wait for it. I'm guessing that after 'The Astonishing Live' the band will take a well-deserved short break in which, hopefully, JP can get his mind out of DT for a while and record his material. I saw him live in the G3 tour back in 2012 and the new material was amazing. I've always thought JP's solo music has an incredible balance between riffy, heavily rhythmical sections and melodic bliss. Suspended Animation is awesome, and I'm crossing my fingers so it happens sometime throughout 2017 or 2018.