I really don't understand why people think bringing MP back is going to change anything. He never wrote the music.
He did not, but between him and Petrucci it was already two metalheads in the band - probably having more leverage regarding the musical direction. I love Mike (M) and I don't want to see him go, but after the (for me) pretty much immaculate string SDOIT -> BCASL, where
every album was great, IMHO, the "direction" with Mangini leaves something to be desired, even if I really loved and still love ADTOE.
The Astonishing was a misstep, a rather enjoyable, occasionaly great one, but a misstep nonetheless. I'm looking forward to the next album, however it might sound.
It might be a coincidence, but there's also that "special" feeling the band had with P, with the bootlegs and demos and stories, rotating setlists etc. That's pretty much gone.
On the other hand, when I see all those "BRNG PROTNOY BAK M&$#$@+#", I get rather angry.