No matter where the test has been, it seems like they will only be there for a few years. Phoenix and Tucson used to be the hot setup, then that died down a bit, then everyone went to Vegas for a few years, then that died down, then everyone went to PBIR and now that is dying down too. I would think that they would prefer to test at Phoenix or Vegas, at least the data collected could be applicable in a race situation.
It also seems to me, that whenever they start advertising it as an "event" and sell tickets is when the teams start to look for somewhere else to test, or even worse, they do their testing in the middle of the week. That happened to me a few times here in Vegas, pay $20 to get in on Saturday or Sunday (or both) and see all of the team's rigs in the pit area and they might make one 330ft squirt. Then read online about the multiple laps and big numbers put up on Monday and Tuesday when no one was there to see it, or would have been allowed in to see it.