For non-marquee teams to get consideration for a NC game, it is usually a 2-3 year process anyway. What I mean by that is it typically takes a solid 9 or 10 win season + a bowl win, with a lot of guys returning, to get the national attention, and then an undefeated season with a decent OOC schedule the following year to get into the title mix. I don't see it as being different under the 4 (8) team tourney scenario.
It was the same back in 1987. Had SU had a 9 win season and a bowl in '86, the '87 team wouldn't have had to slowly climb into the rankings early on. It took 4 weeks just to break into the rankings. If you start in the top 20, it's a lot easier to move up by winning early but you can't start out in the top 20 unless you have the formula I outlined above.