I would say that chances are Werdum would end up on his back.
On his back I say this is a real close fight. I mean Nogueria spent a good amount of time in Werdum's guard doing almost zero damage and they went to the ground mostly after Nogueira had just stunned Werdum. Gonzaga is probably more powerful than Nogueira but is also slower than Nog. I could see Werdum throwing a bunch of subs and getting this SD since Diego got a judge to give him the Sanchez/Fitch fight and I think this will be much closer.
However Werdum did get Aleks E. down who is much bigger than Gonzaga. If Werdum somehow gets on top I think this is no contest on the ground. Werdum really out fought Nogueira when he was on top and he made Aleks E. look like an kid with that arm triangle.