What I heard was not related to the timing directly, but what I heard and believe to be true indicates to me that all the buzz you're hearing right now about the big confab in Tampa is actually a bit behind.
I'm speculating with this part. I believe Gruden had already signed off. I believe the big confab in Tampa today, assuming it took place as rumored, was to reach a consensus on essentially a 20 year plan for the program, which would likely include life after Gruden. That's why it was a "pivotal" moment. I think the long term plan involves individuals who may be coming on staff as Gruden's assistants.
In any event, I don't see how they keep the lid on past this weekend, much less after Vandy.
Everything aside from the direct info I got on Gruden himself signing is JMO.