How big a breaker / circuit you can put in depends on your electrical load calculation. You can ask your electrician about putting in a larger circuit but as you already know, it wont do anything for your incoming model 3. It either maxes out at 32 amps or 48 amps depending on which one you got. Since you dont have a long run, and you would likely have to have your electrician come back out anyway if you were going to get another tesla and wanted to charge both at the same time, I say just go with the 60amp for now, and address later "later".