Include background to ideas for future work in related work chapter of master thesis?
While is always interesting to venture in new areas while writing your thesis, the overall advise I usually get is to keep a solid straight line story, this way the readers won't feel confused on why did you put certain stuff that you did not use at all.

The main objective of the related work, should be to put your own work into context with respect to your peers, but your present work, not your future work. You would be basically citing your future work, which would not be good.

You can always write a Future work section that can be as long as you want.

My overall advise when writing your thesis (especially for Masters) is to keep it simple and straight.