The SEC can enjoy it for a short while until other SEC teams screw over SEC teams. Then the B1G starts screwing over SAeC teams. Then the ACC. The final straw is when Iowa Sta screws over an SAeC team, that is when the calls for a stronger NCAA (or another organization to be named later) that will keep everything fair.*
Who knows, maybe there will be an organization that has real teeth holding all schools to the same standards.
I think an All-SEC/Only SEC conference and championship would be novel for a few years, but after several years of the majority of the nation and CFB fans screaming that the SEC is pansy and cannot play football with others they will have to rejoin the majority. Several in the SEC have already indicated that they cannot go to a P2 without significant expansion, we can reasonably conclude that they also mean the SEC cannot really create a stand alone SEC league.
*Fair = SEC gains and holds an advantage over other conferences.