It will be interesting if it's just Gonzaga MBB or all their sports join the Big12. And by adding Gonzaga, do we see other non-football school(s) added to expose the Big12 to new markets. There could be a number of schools from the Big East that would make sense.
It's not the norm for a school to bounce between conferences like UConn, but there could be contractual language spelling out conditions for Gonzaga's continued Big12 membership.
But at this time UCLA, Arizona and Gonzaga are the 3 biggest college basketball brands on the west coast. So adding Gonzaga seems like a win/win as I would expect ESPN & FOX are on board.