Ugh, thought the reveal was lame as hell myself. Dexter has been trying to track down Gellar for ages, yet he wastes all that time setting up his kill room and talking to his dad first (just so he doesn't get to see Travis talking to himself), and then he descends into a basement that has, surprise surprise, Gellar dead in a freezer (just so he can be trapped down there by Travis).
It was just all so painfully obvious and contrived.
The shame of it is, the basic idea of Travis and Gellar was a good
one. The writers just did an absolutely terrible job of disguising it.
Sadly, I think I really have to agree with this assessment of the series right now. At this point most of the originality is gone, and it's starting to feel like just another procedural.