After thinking about this a little more…
PSU - In with a win or a loss by either Idaho or Weber. Only the 2-way tie with SUU for 8th. leaves them out. It's theoretically possible for PSU to still win common games with SUU, but not really because EWU & Weber would both have to win and that's impossible since they play each other.
ID - The Vandals have a similar situation to PSU, except the 3-way tie with SUU & PSU leaves them out. They need a win or an SUU loss or a Weber loss.
WEB - Weber loses any tiebreaker for the last tournament spot (they were swept by SUU), so they need a win or a Suutah loss.
SUU - They now have a straight-up playoff game: win & they're in, lose & they're out. The T-Birds will win any tiebreaker.
If I had to predict, I would take Idaho as the odd-team out that chokes away the tourney spot. All the games involving these teams are pretty close to coin flips, though.