The guy has crushed the competition in his weight class. WEC has arguably the most talented FW's in the sport and he's taken them out no problem. The only people really left for him to fight in the WEC are Josh Grispi (IF he wins his next fight) and possibly Mark Hominick. Chad Mendes has done well recently, but poses no real threat to Aldo and and once again needs to win his next fight in order to prove where he is in terms of contention.
So with the next FW contender pretty much being a cluster fuck and Aldo already beating the top dogs in his division, in arguably the best organization in terms of FW competition, I think it would be safe to put him in top 5 P4P rankings.