I would pay and get secure position. As a student employee under SHDS for the upcoming year, I have not heard anything from the office. All job trainings are under assumption of school will open in fall and get physical training before the fall quarter starts. Since UCD has not made official announcement on it, I will rather secure a place in case of in-person classes. Otherwise, I guess school will refund or credit on your school account.

If you are concerned, for personal opinion, I would look for how UCB reacts for their fall semester. UCB has earlier start of school year and UCB and UCD are pretty close, so Davis is likely to follow Berkeley's decision.