If the top-5 are the only ones with a chance (based on historical results) to win, here's what I think a win will mean to their legacy:
T-5
Simpson: Lock HOF'er w/ 2 majors & a Players (That's kinda amazing to say. Would be similar to Kaymer w/ out the 2012 Ryder Cup kicker)
Poulter: Virtual Lock HOF'er w/ 1 major & stellar Ryder Cup record
4th
Koepka: Approaching legend status w/ 3 legs down and wins in 4 of last 7 major starts; Possibly moves to #1
T-2
Woods: 15th major; 81st win (1 back of Snead I believe); Might break the internet
Finau: Long-time coming; Hard to fathom he's one only 1 time (on a opposite field event in P.R. iirc); More raw talent than all but 4-5 guys perhaps
1
Molinari: Lock HOF'er: A career like Kaymer's but actually improving (2 majors, 1 WGC for each; Ryder Cup warriors, Players (Kaymer) vs. BMW (Molinari); Should move into top-4 in OWGR.