To set a few issues straight here we will assume you need to be undefeated to make the NCG. (Let's assume that, say, the SEC or whoever champ with 1 loss doesn't beat out a non BCS undefeated team for now. That will be revisited late in the season).
One-loss teams and the like will be visited later as the season plays out.
I will show who is left in the hunt in each conference and what the conference and team chances of reaching the promised land look like.
I am ordering the conferences and teams randomly for now, as the season progresses it will be by strength.
Rundown: After Week 4 there will be 3 or 4 teams left 6 of those teams play eachother and LSU plays an undefeated West Virginia team. Whichever of those survive must be taken seriously.
Big Ten (6)
Rundown: Ohio State is a favourite for the NCG and them along with struggling Wisconsin are probably the favourites to make a run. While some teams like Michigan and Michigan State face a lot of skepticism and Indiana is expected to crash sooner than later, all teams are expected to win this week before entering conference play. Northwestern may have the only significant obstacle hosting Central Michigan. We still need to see what this program can do especially without Kafka.
PAC 10 (3)
Rundown: This week all 3 teams will face some opponents they should beat but could easily lose against. By looking at schedules Arizona probably has the best chance to make it the furthest but Oct 2nd will be the game to watch when this list will be reduced when Oregon hosts Stanford, that is if they don't lose trap games this week.
Big 12 (7)
Rundown: This list will likely stay the same next week. The only Gimme for this week appears to be Nebraska but all the other teams are favourites and should win but losing would not be a fantasy considering the matchups. Week 5 will be similar to the SEC this week.
Big East (2)
Rundown: This is sad for the Big East but West Virginia got lucky and now has a shot to let everyone forget Marshall when they go to LSU. Rutgers likely doesn't have a chance but if they can beat North Carolina perhaps they can get the fortune to squeeze some close wins to make it an interesting season finale vs West Virginia
North Carolina State
Rundown: Perhaps even worse than the Big East Situation. Many don't have either of these teams winning either of their next two games. Both play Virginia Tech, while NC State goes to Georgia Tech and Boston College hosts Notre Dame. However if things works out they will meet eachother in 3 weeks time and perhaps 1 of them will carry the ACC torch on the road to the NCG. That's not saying the rest of their schedules will be easier though.
Rundown: For now both appear legit. Utah will need to dominate before facing up to 5 teams that could be tough to end the season, @Air force, TCU, @ Notre Dame, @ San Diego State, BYU. TCU is the favourite here however and looking ahead of such games as hosting BYU and Air force, it appears that @Utah will be the all important game.
Rundown: The MWC must be happy. Well at least they will be in the offseason. Boise State is the clear cut favourite. All these teams face tough opponents this week. Boise hosts Oregon State and probably needs to beat them better than TCU did to make a statement. Fresno is going to Ole Miss and Nevada goes to Provo to play BYU. Assuming they are the cream of the conference and all win this week they should all theoretically, in a perfect world, go undefeated until the last quarter of the season when they all play eachother.
Rundown: Temple is the last hope of the minor progams. Sure the WAC and perhaps MWC aren't major themselves but the teams involved are the traditional powers in those conferences. Last week Temple defeated a Big East team for the first time since being kicked out of the conference. This week they face a Penn State team that is still trying to find their chemistry but usually pummel the Owls. If by some miracle they win they should go undefeated until the conference championship.
Again reminder when I say should it is always in a "perfect world".
So looking at it now the healthiest* conferences looking at teams and schedules appear to be the:
maybe the Big Ten (sched and perceived weak undefeated teams)
*By healthiest it means most likely to have undefeated teams and more undefeated teams expected to go far. They are not in any order above except maybe the Big Ten.