Well, we don't really know what kind of "upgrade" Surfer got. He has an immense amount of power to begin with, if Galactus were to simply remove his personal psychological restrictions, he would be a great force.
Also, who's to say Thanos and Surfer are going to fight anyways? Thanos has no allegience to Annihilus, he seems to be playing him actually, "allying" himself simply to extract a fee of Annihilus.
Also, a significant event for those Heralds of Galactus fans, Morg's dead.
So that puts Air-Walker, Morg and Nova underground.
Terrax is Annihilus' captive.
The Fallen One is under Thanos' thrall.
Firelord, Red Shift and Stardust have banded together.
Silver Surfer is again chilling with Galactus.