For a long time FBS college football was commonly divided between the Power 5 conferences and the G5. While some P5 conferences had up or down years, there was a clear gap between them and the G5. With the implosion of the PAC-12, many have switched to referring to the P4 and the G6 or sometimes the G5/6.

But I think though that there is now, already, a clear split between the top 2 or "P2" conferences, that is the B1G and the SEC (with independent Notre Dame thrown in) and the remaining conferences. The ACC and the Big12 are still clearly better than the G6, but also clearly on a lower level than the P2. I think it would make more sense to talk about the P2 and the G8. 

The P2 get more money, recruit better, have better metrics and are simply playing on a higher level than the G8. The only current or future foreseeable national championship contenders outside the P2 are Notre Dame, Clemson and in a good year perhaps FSU. Once Clemson and FSU can escape the ACC, the gap is only likely to grow wider.

Going forward the G8 aren't likely to send many teams to the playoffs other than automatic qualifiers whatever the playoff format.

I think the time for the P2/G8 has come.

(Mod Edit: Moved to the College Sports Forum.)