Well, 2.74 is pretty bad, but I don't think your application will be weakened at all expressly by the fact that you're taking the PCAT in January. I think what you meant to ask is by how much your application would be improved if your PCAT score was available sooner - Quite a lot, ostensibly, if you score(d) well on it.
But, I mean, no one can ultimately say 100% for sure what could happen. NOt even one AdCom could say, since every school and maybe even every AdCom will be looking for way different things.