Certainly - and it could happen this year
Both the Big12 and the ACC will likely only get ione spot (their CCG winner).
Heading into the CCG for each, there is a good chance that one of the contestants will be in the Top 12, and the other will not.... so upsets (by ranking) in either of those games probably means the CCG loser drops out of the top 12
Example... Miami remains in the top 12 - and plays, lets say, SMU or Clemson in the ACCCCG and loses - Miami is likely out
Right now, in the Big 12, I am not sure if any of them are top 12 - but one likely will be headed into the CCG (likely BYU or Colorado - possibly ASU). If the higher ranked team loses in the CCG, same deal.
Losing the CCG could (but less likely) knock out an SEC team as well..... but much less likely since they will be getting 4 or 5 in, and I expect the committee will use a lot of discretion to NOT have the CCG loser get knocked out (but it would not be beyond the realm either). Same with the Big10 (or any other conference, moving forward, that will have multiple slots in the playoff)