Yes, it depends on Mac bulking up A LOT - Mac tried bulking up for 2 years and it did not work. That is why it is interesting to see if it ever happens.
Sometimes a shorter guy has a tighter motion so he can throw with more velocity, and some of the taller QBs do not have the body type to bulk up so they can never throw on a rope. After 3 years, everyone in the NFL (the professionals) has voiced their opinion by offering a 6th or 7th rounder for Mac. Offering a 6th or 7th rounder is basically saying that the other 31 GMs and their staffs think it is a very long shot that Mac will be able to bulk up.
But we still have posters here thinking that the 32 GMs in the league are wrong. Amazing.