It should definitely stay as Mario for like all the reasons already stated. It would just be odd to change it to Link at this point, Mario has beent he face of Nintendo for so long. Plus, I think Mario is a better fit. Link only seems to find his way to certain genres of games (fighting, action, adventure, etc.) whereas Mario has been in these genres, plus like every other genre (an exaggeration, I'm sure, but it's still been a lot more). Mario is much more well-rounded in this sense, so everyone can relate to himm in some way, even if they dont' like him. Link.... not so much.