Certainly could be true.
But it also may not be...won't know until April/May.
So far, this team is averaging more points than last years team. They are giving up the same amount of points. Their FG% is up while their FG% defense is the same. Their 3pt% is way up, 3pt% def is the same. Turnovers are the same, both ways. Rebounding% is essentially the same but their rebounding is down a little more than 1 per game.
So, offense is up, def is the same and rebounding is barely down.
Edit: assists are also way up.
Even if the Thunder win it all, that won't mean that they wouldn't have been better with Harden.
I've already pointed out that the comparison of this years team vs last year isn't particularly relevant regarding this trade. If the Thunder had Harden instead of Martin, their numbers would have been better too, because you know, they would have 3 top 20 players in the league plus Ibaka at age 24 or younger and guys at that age normally get better.