Loaded question. He hasn't lost in the UFC obviously. I think he looks like a killer. But at the same time there is legitimate questions.
The questions revolve around him not fighting a single elite fighter yet. His best wins are Dodson/Rivera/Faber. Three solid guys, two are washed to varying degrees, all 3 are actually sneaky old as balls for the division.
Aldo probably beat Moraes and got robbed of a decision. At least we know he's still right there with the elites based on that, and obviously was at 145. I think that's the only question really is the level of competition Yan has faced. He's nearly undefeated, avenged his only lost, never lost in the UFC. But has he ever beat a top 5 guy? No.