No one is raiding the Pac 12, and at this point it doesn't appear that the Pac 12 will ever raid the Big 12. Boise State and BYU are the only two candidates for expansion in the West. Boise State is a national brand with good attendance in a decent sized city. I believe they are expanding the stadium, and with a better schedule, would probably expand it again. The basketball program sucks but would probably still win 5 or 6 conference games in a Pac 12 that is pretty awful top to bottom. I believe Boise does play a sport or two in the Pac 12 already.
BYU is a tremendous national program with a large following and is strong in football and basketball. It would be a strong financial addition to any league, particularly one like the PAC 12 that has its own network, but its leadership is a giant pain in the to work with, and it has embarked on this independence mission that seems like program seppuku to me.
Boise would be the third best football program in the Pac 12, and BYU would be about the 5th or 6th. BYU would have won the league in basketball the last two years. Those two are it though. Everyone else out there is such a huge drop off in terms of fan interest and national presence that they are not worth discussing.