Personally, I don't think that PRIDE is going to come back. UFC has already migrated a lot of the top talent and big names to itself (as in, fighters that were identifiable as PRIDE fighters) and the title unification just SCREAMS that they are trying to phase out PRIDE. I really doubt that Zuffa would alternate title defenses between two different promotions, it just doesn't translate to good business.
Is whoever is left under PRIDE contract even worth watching? Let's break it down:
Heavyweights
UFC absolutely RAPED PRIDE of their heavyweight division. The top heavyweights of who are left are like Aleksander Emilianenko, who is good, but isn't that great; Kaziyuki Fujita, who is fun to watch because he can take a hit like no one else, but has lost to all the top guys; Kevin Randleman, at one time UFC champ, but isn't completely relevant these days; and Mark Coleman who is WAY past his prime. Not exactly a money division. The title is also on a free agent.
Middleweight (205)
PRIDE champ Dan Henderson is unifying the title with UFC champ Rampage Jackson (another PRIDE guy) in September. Vitor Belfort, Shogun Rua, and Wanderlei Silva are all fighting in UFC soon, so this division is really dead.
Welterweight
They still have Dennis Kang and Phil Baroni, so that's something. Dan Henderson the champ, though, and he is in UFC now.
Lightweight
Hey a division that still has its champ! With Takanori Gomi, Gilbert Melendez, Hayato Sakurai et al, this is still a really good division and the only division that has fighters that can rival UFC in terms of quality right now. I expect UFC to bring all these guys in, especially with UFC champ Sean Sherk recently failing a steroid test.
So really at this point, the name PRIDE has lost all its value as all its top names are currently at the top of the UFC, and if Zuffa decides to hold a PRIDE how in Japan, I expect they will only use second rate guys they don't feel like brining into the UFC and it will ultimately become a place for guys not "good enough" for the UFC to fight.
Really, I expect, and hope, that UFC just starts running a couple shows a year in Japan to keep that audience happy, because right now "PRIDE" coming back would just be a slap in the face.