I think Dana knows it's now or never. Unless Silva wants to fight 3 times this year and do Okami shortly after GSP fights Shields?
From a business perspective there's not much point risking losing the opportunity for this superfight by facing Silva off with Okami, Sonnen or anyone else. One of these guys is going to beat Anderson soon so it may as well be GSP in what will be the biggest fight ever.
Okami should get the winner of GSP and Silva, which will be GSP, and then Anderson can either work his way back to a title shot or go to 205 and hope he avoids all the wrestlers who wouldn't get subbed out like Sonnen and leaky gas tank Lutter.
Anderson Silva has lit the UFC up for years but his fall is coming, he just hasn't met a good takedown artist with equally good top control and sub defense yet. Sonnen was almost that guy, he did it for almost 25 minutes. I have no doubt GSP would finish the job and I think the likes of Rashad Evans would do too.
I think this is definately the time to do this fight. It would be a record-breaking draw, and there is no point in waiting any longer. Silva isn't old yet, but he is 35, which for the fight game is definitely closing in on the downhill side of your career (Couture is a notable exception).
I'm not sure Silva is quite as vulnerable to wrestling as Sonnen made him look. I think he is weaker on the ground than previously thought, but he looked very uncharacteristically slow in the Sonnen fight. I don't normally give much credence to excuses, like 'my ribs were hurt' after a fight, but it did look like something was wrong with Silva, he looked terrible.
Silva will obviously lose if he fights long enough, as anyone will, but the idea that Rashad Evans could beat him right now just makes me laugh out loud. GSP has a chance, but Evans can't do anything better than GSP, except weigh in heavier. GSP is far more explosive, has better top control and better striking, although perhaps less ko power. Silva would eat Evans alive.