"A semester or so" reasonably covers until September 2021. I can't see the world standing for social distancing that long, and as such covid will spread throughout the population just like Polio, TB and uncurable/vaccinable diseases of the past. IFR of covid for undergrads is about 0.002-0.005%, so 1 in 20k-50k.

Chance of death for a 20 year old in the UK is about 1 in 4k, so you're 5-10 times more likely to die for some other reason than covid.

Indeed by moving away from home you're less likely to infect older parents, so it's a rational call.

There are multiple vaccine candidates that have passed phase I trials, have demonstrated they produce antibodies in humans, and have demonstrated they are successful in animal challenge trials. The chance's are good that we have a working vaccine by end of year, and the chances are very good that we have one sometime next year.

In the unlikely event it turns out that we can't develop a vaccine in the near future, we'll have to just deal with the disease long term. If we try to keep the world economy shut down for more than a few months at a time, we'll kill more people than COVID would. And as other people have pointed out, college students are very low risk.