Sources inform Bloody Elbow that a number of fighters waived their right to renegotiate and agreed to transfer their contracts over to Strikeforce as part of the closing of the deal. However, a significant number of fighters chose not to take that position, and will now either renegotiate with Strikeforce or attempt to find somewhere else to fight.
Among those that are not waiving rights to renegotiate are fighters that Zuffa is interested in. Zuffa only has direct interest in a small number of fighters that were contracted to ProElite. These fighters include Gina Carano, Jake Shields, and Robbie Lawler. I can confirm that Robbie Lawler is actually negotiating with Strikeforce, which means he is not a part of the group that chose to waive its rights. I have no confirmation on the intentions of Shields or Carano, but it is almost certain that Carano has not waived rights to renegotiate or look elsewhere. Zuffa interest in Gina is higher than ever now, and her contract at ProElite was outrageously low considering her value.
One big name that nobody has talked about is Kimbo Slice. His contract was worth a lot of money, and it's unclear whether he is still worth that kind of money. He obviously still has name value, and could draw as an undercard attraction. Zuffa certainly has no interest in him, but he does have value.
I spoke with Strikeforce and they were unable to confirm or deny details on contracts, except to say that the issue is very complicated. They did however let me know that there will be a major conference call next week to address these issues.
UPDATE: There are a number of reports saying all the contracts came with the deal. The caveat is that you can put anything in a deal, that doesn't change the fact that personal service contracts are non-transferrable. If someone that didn't waive their rights tries to leave, Strikeforce won't have much of a legal case against them. However, my impression is all the fighters are on good terms with Strikeforce and open to renegotiation.
All you need to know is that Strikeforce is currently renegotiating with a number of people, and wouldn't be doing that if they simply got the contracts as is and didn't have to do anything to legally cement the deals. The best analogy I can think of is to a no-compete clause in California. You can put it in an employee's contract, and they might sign it, but if it ever goes to court it simply doesn't hold water.