A Siri enabled TV doesn't sound like that great of an idea just yet, there is still the need for a remote control because there are a lot of functions that would be difficult to use with Siri.
I bought a Logitech Harmony 700 to tie all of my different remotes together, it makes more sense for the Apple TV to have a smart programmable remote.
The Apple TV interface will be a thing of beauty, I'm sure, but the UI for just about everything else is pretty crappy.
The solution to that problem would seem to be an Apple interface that dominates that of peripherals and an intelligent enough programmable remote to replace all other required remotes.
The Harmony is a nice remote but Logitech went with a cheap screen and the UI, otherwise it would be the perfect replacement for 5 other remotes.
If Apple can succeed where Logitech has done a pretty mediocre job then they can effectively improve the user interface across all peripherals.