Most current and future lenses are going to have the focus motor included so that they can work on all Nikon bodies (same as Canon lenses do now). There are only a few which don't have this.
You are worried about saving some money on glass but are willing to spend loads on a new body so you can save, this doesn't make sense. Again, cheap glass on good body = mediocre results, good glass on cheap body = much better results.
To me it is false economy to go with your method of thinking (and that is as a Canon shooter so not trying to force you to stay Nikon for the sake of it).