In my opinion, DT already proved who they are and what they can do. They still are influential, too, so that's bonus points. To be honest, innovation has to come from new bands, which have a more fresh view of Prog music.
Haken are the perfect successors of DT (style wise), if you ask me.
Caligula's Horse made a very interesting twist in the Dream Theater-y sound, adding some Jazz (mostly harmonically), Djent, and even Alternative Rock influences -the band defines their sound as Progressive Alternative Rock-.
DispersE released Foreword, which, stylistically, is one of the most interesting/original albums of the decade, IMO; samples -vocals and sounds- used musically, Electronic and Pop influences, Ambient parts, Holdsworth-esque solos, Djent... all over a Prog ala Dream Theater sound.
Leprous started with a very DT-esque style, and now they're unique.
(I'm only talking about DT-y bands, because there's also bands like Animals As Leaders and TesseracT who are unique).
My point is, Dream Theater has +30 years playing music, and many new bands and things appeared since they defined their own sound. Their tastes and influences are already defined, too. So, I doubt that they can innovate without doing a 180° turn or something (and AFAIK, Pink Floyd is the only band who pulled off that perfectly). New bands are playing with other new bands, and they have some kind of feedback going on; different worlds.