I would be astonished if Donald Trump left office without a presidential pardon. How he secures it is a purely mechanical question. Nothing in the text of Article Two suggests that he could not simply issue a pardon on his own behalf. It is also possible to imagine him delegating the power to Mike Pence under the terms of the 25th amendment. (Another, more audacious scenario involves Trump resigning just before Inauguration Day, making Pence rather than Joe Biden our 46th president, albeit for a single day. Mother would be proud.)
So much for whether Trump “can.” A better question is whether he should.