What an exhausting thread... there are 2 camps here.
Those who say 4 and those who say 8. If you say 4, then #5 could legitimately be left out, even though #5 could be just as good. #8 may not be, but you can't have a 5 team playoff. So you expand to 8 and if #6-8 suck as bad as people are saying, they will never advance. But it allows #5 to still play for all the marbles, and deservedly so.
I honestly don't see a ton of downside, even if 3 SEC teams are in. Going back the last 5 years, there would be 2 years where 3 SEC teams are in, 2 years when only 1 SEC team is in, and 1 year where 2 SEC teams are in.
Conversely, the last 3 years, the B1G would have 2 teams in each year. Before that we didn't have Meyer at tOSU, and Dantonio didn't have MSU humming yet... but moving forward, our conference is so much stronger now. We will almost always have 2 teams in and occasionally 3...
8 team playoff will not ruin the game, imho.