Yes, but he'll only talk about himself, insult the state for voting Biden, and not help Perdue or Loeffler at all.
They'll have to do some intense cost/benefit analysis to decide whether to attend the rallies at all. It may be a lose-lose situation for them.
Anecdotally I heard that Trump's visits to Louisiana during Bel Edwards' 2019 reelection bid actually galvanized turnout for Democrats.
With the loss of suburban voters, I don't believe that off-year elections are guaranteed to favor the GOP anymore, even after a Biden victory.