Well, first, some schools are going online only for the latter half of the semester. But my understanding of the current guidance is that this is not enough to meet the in-person requirements, and so students may have to leave anyway and miss that half. Second, intl. travel is highly disrupted already and will continue being so. Some countries will fare worse under covid than others, and so students may get stuck, even after their school states are doing better. No guidance was given on students from travel ban countries, who were already here after the travel bans. Third, student visas expire. Visa politics are very volatile lately. Summing up, many people are now subject to gratuitous uncertainty about whether they'll be able to come back in at all over the next 12 months. Suppose you have to leave, a lot of people have already signed leases, etc.

Finally, the guidance so far is quite ambiguous. It is not clear who is able to remain and who won't, and my department sent an email basically saying they are waiting for extra information to know what's going on. That already is bad in itself.

An additional challenge is that classes will, almost certainly, be scheduled based on "local time". Students attending from other countries may find themselves needing to significantly time-shift their studies.

This is definitely a major issue - the US has a lot of students who come in from China, which would require a very significant time shift. Those students may also not be able to access the digital resources they need for class due to internet censorship, or they may simply be unable to join live class sessions due to latency or overall speed issues.

I had overlooked the potential impact of internet censorship. It seems like it would be very hard to take a graduate-level class without access to resources like Google Scholar.

Ah, China...I see

Those are excellent points, thank you

Ah, optimism and assumptions.