We're in a similar position - thinking about thinking, if you will. It really does need a lot of variables to be taken into account. We've decided for now that the next steps taken by daughter and SIL will be the deciding point - if they move, then we will look to move near-ish (maybe even the whole granny flat shebang!).
I think that the wrap-around retirement villages are a good idea but they are businesses, their costs will go up not down, and they will inevitably change hands.
Maybe we should all get together and form a collective.