I'd say Williams is the most likely to no flame out, simply because of his size. The taller you are, the more likely you are to be in the league.
Here are some "short" Power Forwards in the league.
6'5" Marqus Blakely
6'7" Jeff Adrien, Jon Brockman, Da'Sean Butler
6'8" Paul Millsap, Renaldo Balkman, Brandon Bass, Dejuan Blair, Derrick Brown, Dante Cunningham
6'9" Darrell Arthur, Carlos Boozer, Elton Brand, Derrick Caracter, Brian Cook
This is just through the letter "C" on ESPN.com. Admittedly not many of these are stars, but they have stuck around.
Other than Enes Kanter (who hasn't played in the US), the rest on the list are guards under 6'4, and some of whom haven't proven themselves in college.