Omicron means an exponential increase in cases, and now this is also occurring in the South (especially Florida).
Most Ivy league schools (and schools outside the US) have already moved their January classes online.
Vaxxing is no longer a silver bullet. Your students will get sick this month, even the vaxxed ones and the ones who already had COVID. They might not even get back to campus with increasing flight cancellations and border restrictions.
From a liability standpoint, and from a business standpoint, it just doesn't make sense to have people on campus in January. You already have the money for the dorms, this isn't August.