When it was just the leftover 8, every one of the Big 12 schools looked around to see if there was anywhere else they could go. Some of them did so pretty cravenly even.
The reason WVU, Kansas St, Kansas, TCU, Iowa St, Okla St etc didn't bolt was because nobody wanted them. But they were motivated to go.
So are they going to be any more motivated if Memphis comes in? Maybe. But will they have any better options? Probably not