Not all of these teams in front of ISU are running the table. Many of them even have at least one if not two games against each other. An 11-2 ISU team may be on the outside looking in when it comes to CFP but it certainly isn't out of the question they get in.
Possible maybe... but extremely unlikely. If they can come up with a reason to leave ISU out they will... two losses to iowa and texas make it really easy to look past them. But here is a scenario for you:
Pac12: Stanford only loses to ND, Stanford beats USC in Conf title game (P12 Eliminated, with 3 loss Stanford team)
ACC: NC State beats Clemson, Miami loses to ND & VT, NC State defeats VT in ACC title game (ACC eliminated with 3 loss NCSU, maybe)
SEC: UGA loses twice in the regular season (I think they will need 3 losses to move them behind ISU), let's say Auburn and GT (just pick two), then undefeated Alabama destroys them in SEC title (Alabama is in, UGA is out)
Big 10: Wisconsin loses a game prior to the title, OSU beats Wisconsin in the title game, and PSU loses to MSU or someone else (OSU in, 2 loss Wisconsin out)
ND: Wins out giving Miami and Stanford losses along the way (ND in)
So, now you have ND, Alabama, and OSU in the playoff. One spot left for a B12 champ... maybe even a 2 loss ISU (no chance for a 3 loss B12 champ). Then, given the unlikely scenario above, ISU would be compared to B10: 2 Loss PSU, 2 Loss Wisconsin, PAC12: 3 Loss USC or Stanford, ACC: 2 Loss Clemson, VT, and Miami, and 3 Loss NC State, SEC: 3 Loss UGA, and potentially UCF if undefeated.
Do they get in? Not sure, the committee clearly loves clemson. Even if they lose to NC State this weekend do they drop behind ISU? If ISU wins out, would they pass them? What about PSU? I think UGA would need 3 losses, if not, they would likely put a 2 loss SEC title game loser in before ISU. I think PSU needs to lose another game as well. A one loss PSU would also likely knock ISU out. Net, ISU needs a lot of help that is very unlikely. If it does happen, the committee could still leave them on the sideline. If you are ISU, you need to go 13-0 and hope that you are one of only 4 undefeated teams. If not, it is really hard to get in. See Baylor/TCU (2014), OSU (2011)...