while I myself love uBlock and have been using it for over a year now, I’m not sure whether adding it to the TBB would really make sense or be feasible. First and foremost, at the moment the TBB seems to be downloaded directly from the servers of the Tor project, not from another central place, which means that if an adblocker of any kind would be to be included, without being a part of the TBB, this would have to be changed. This also means, that someone would have to maintain this browser. Personally, I’m using the JondoFox browser, by Jondonym over the TBB, as it is far easier to customise. It also comes with an adblocker, though again, it’s ABP, not uBlock or some other open solution. Adding to all of this, we need to ask ourself the question whether adding an adblocker would be necessary. Cookies get cleared after every session, NoScript actually blocks 99% of all ads, as well as tracking methods and thanks to the newly added sliders in TBB 5, choosing your level of security is easier then ever. Also, the newest versions of Firefox include a new private mode so “advanced”, pretty much any ad gets blocked, because of its tracking nature.
However, all of this is only my opinion and you may feel completely different,