Just speaking for myself here, but, enabling the use of SourceTree as a VS extension would be pretty slick. Perhaps open sourcing the lower levels of abstraction so other projects like the one above could collaborate. There's surely plenty of work to do to enable that so I'm not sure if I'd expect to see anything like that any time soon.
https://bitbucket.org/lmn/visualhg2/wiki/Home
http://visualhg.codeplex.com/
It's kind of demotivating to see all action happening in github-land.
PS: I am not a paying customer at the moment.