Yeah, that situation got awkward quickly for San Diego State. I can’t imagine they would do that unless they had a pretty good idea they were going to join another conference soon.
I suspect SDSU has a standing offer from the Big12, and a contingent offer from the PAC12. So I suspect they give their notice, and figure that worst case scenario, they join the Big12 in August or September, if things don’t materialize with the PAC12.