This is perhaps why the cautious reopening plan is a good approach but I don't think a big case rise will happen.It's probably inevitable that cases will actually go up now that schools are opening and when other businesses open, but as long as the death toll keeps dropping that's as good as it's going to get.
We saw a very low uptick in cases after lockdown 1 last year so there is definitely some seasonal aspect to this virus which suggests a rapid increase in cases probably won't happen. It took 5 months to go from around 1,000 cases in May to 10,000 in October last year despite pretty much everything being open by the start of July.
Hopefully by the time cases begin to increase the vast majority of remaining unvaccinated people will be done (end of May) so the effect will flatten. Once that happens there is no reason to not reopen everything on the understanding that less cases will be reported because no-one should be getting ill enough to present for testing.