Assuncao by decision. I think he breaks the streak. Their first fight was very competitive, but Assuncao has improved a lot more than Faber since then, especially with his striking. He is one of the more technical strikers in the sport nIow and is a legit Top-15 p4p guy, imo. I think this will be the fight to really showcase it, and the biggest worry I think will be his conditioning following the ankle injury (hopefully nothing serious), assuming this is a 5-rounder.
I think Faber will struggle with his counter game and pivots, and even though Assuncao has a lot of trouble finding his range when he is the one moving forward, I don't think Faber has the right skill-set to really threaten pulling away on the cards on the feet. But when Assuncao uses his jab (like in the 3rd round against Munhoz) he can be very effective on the front-foot and we might see more of that depending on how Faber approaches this.
His grappling has improved too. When Dillashaw took him down in the first he got up with a nice arm drag and elevation from butterfly guard, then pummeled for the underhook and drove Dillashaw off him. Dillashaw isn't the overall grappler Faber is, but he does some things and set-ups with his wrestling at not a totally different level. Assuncao's escapes from the bottom are very technical and crafty, and his guard passing is still some of the best in the division if he gets to that position (against Lee he had that s-mount transition into the armbar).
Assuncao shouldn't get frustrated if Faber tries to control the distance like he did against McDonald with the pot-shooting, and force him to create openings in other ways. I think he has shown that he won't be set-up so easily by foot traps like the Dillashaw fight showed, so Faber will likely need to show something new. Assuncao will need to have the right game-plan for Faber's right hand, especially the cross counter which along with his understanding of angles, he has gotten better at setting up over the past couple years.