After more reading, some MOAR thoughts...
There is no doubt Dana's interview with Ariel was mostly PR besides breaking the news. The stuff about contracts and needing them to expire is fishy. Plus, by many accounts, expect what's going to happen over the next two years to be similar to WEC.
First, the contracts. Zuffa owns them. Just like Zuffa owned the WEC contracts which a majority of the former WEC guys are continuing to fight on. They didn't need for them to expire to bring them over and book them in the UFC. The detail about needing contracts to expire is only if they truly intend to run both UFC and Strikeforce as separate entities.
Showtime is the big wheel in this deal because there's no reason to believe they are a lot like Versus (minus the rift between their execs and Dana). Zuffa purchased WEC in large part to keep other promotions off of Versus and were able to originally showcase guys who werent prepared for the UFC (Jake Rosholt, Brian Stann, Donald Cerrone, etc.) and it featured lighter weights that weren't in UFC.
As long as Showtime doesn't pull a power play and axe their contract, Zuffa is in a position where may not be able to prevent other brands from being showcased (and it will be increasingly interesting to see if Showtime tries to irk Dana by airing all kinds of MMA besides M-1). So it's the waiting game. By all accounts, 2 years remain on the deal.
As we saw with WEC, the UFC eventually ended up absorbing everyone they wanted. With Strikeforce, will they cherry pick guys who can provide fresh fights? Think Nick Diaz, Gilbert Melendez, Josh Thomson, Tim Kennedy, Robbie Lawler, etc. The only issue is they probably don't want to go full boar in turning SF into a minor leagues type of brand by bringing over a lot of the top talent. So that means, keep it as is with the exception of guys whose contracts expire and can negotiate a new deal (Dan Henderson is one).
More or less, as long as Zuffa has a contractual commitment to provide live MMA content to Showtime, I would not expect them to raid the big talent. They may pluck a guy here or there when necessary to fill a spot (Dana refuted this idea to Ariel), but for the most part, they will keep Strikeforce as is.
If nothing major changes, over time, I'd expect to see the exodus of guys to UFC pending whether or not they don't go on an Arlovski-sized losing streak (guys like Diaz, Melendez, Big Foot, Kharitonov, Woodley, Jacare, Mo, Mousasi, Feijao, Thomson, Kawajiri, Aoki, etc.). In 16 months or so, I wouldn't be surprised if Strikeforce ends up as a talent development type of place with guys who may not be ready for the UFC.
And whenever the deal with Showtime is up, the Strikeforce brand will be as dead as ECW is today.