I like Paul, but as I said in a discussion with a friend lately, he won't be a Welter forever. Running ten miles every day and starving yourself, while your at your metabolis peak would indicate that he will be climbing to 154 and perhaps beyond in the future.
So, I'd suggest for him to make Hay while the sun shines, fight as many Welters as he can and force his claim at the top guys. A rematch win over Margarito would put him in a strong position I feel.