He's not the next D Wade because he's too short. He's listed at 6'3, but he's probably more like 6'1.5 w/o sneakers and guys that height almost never make it at the 2G position in the league. Purvis will likely be a first round draft pick, but the team that drafts him will more than likely attempt to turn him into a full time PG.
Why do people still say this? Westbrook and Rose are pretty money from mid range. As for Wade, you don't put up a 30/5/7 season without a mid range j at 6'4. He was off because he was injured last season, but prime Wade was at least average from mid range if not good (depending on what criteria you're using to judge).
Talking about no shot coming into NBA, not no shot now. Westbrook is one of the best from midrange at this point amd Rose is improved but nothing special shooting wise.