In short, "Yes". One of the benefits of Linux is it's ability to share common libraries/dependencies among different running applications. Because of this, many users are firmly rooted to GTK, QT, KDE , etc. and will refuse to install apps that have dependencies falling outside of their chosen camp. This line of thinking can have very practical benefits on a low resource machine. Imagine three applications, all based in different tool-kits are running on a single computer. Those applications will then need all their own tool-kit libraries loaded into ram in order to function, even though many of those libraries perform similar functions. Now imagine three apps all running on a some computer, but they are all Gnome-based. In this case, all three Gnome apps can share the same libraries in your ram. As you can see, tool-kit loyalty can certainly decrease your ram usage. As well as decrease data transfer from your hard disk as the system will be retrieving less dependencies.
The flip-side to this is that if you have a relatively modern computer you may not notice any difference at all. Multi-core processors, solid-state drives, and gobs of cheap ram make many of these considerations moot. Your biggest concern may actually be that a KDE app doesn't look "right" on your GTK+ desktop.
In the final analysis, you would have to gauge yourself as to whether your machine is bogging down under the load. If it still feels like normal, then don't worry about it. Enjoy using the applications you like. If it's dragging, then you may have to reconsider looking at some GTK options for future use. Good luck, hope this helps!
A few months ago, Phoronix posted some benchmark results of 3D performance with different desktop environments. You can find the article here: http://www.phoronix.com/scan.php?page=article&item=ubuntu_1204_desktops
Do note that these were results from Ubuntu 12.04 so results may be a bit different in 12.10 or later. As you can see from the results, Unity tends to eat away a little bit more then other DE's. So, if you are going to make a system purely for gaming, it looks like using the Xfce (Xubuntu) environment will provide the best performance.
Best Answer
No
Simply based on the interface and goal of the Ubuntu TV.
Source
The Ubuntu TV interface is a Desktop Environment designed to emulate (and built on top of a fork of) the Unity-2D. Since the Unity interface is Canonical's consistent user experience in the computing world the thought of re-designing Ubuntu TV to mimic other Desktop Environments will likely not be on the short list of goals for Ubuntu TV.
Only time will tell, but other DE maintainers such as KDE, XFCE, etc may develop and modify the Ubuntu TV to mimic their style Destkop Environment.