Congratulations on your new home! In a perfect world we would recommend doing the all construction work now and enjoying the new bath for your future in the home. The current tub doesn't work with the description of style you'd like to live with. Maybe you can redo the tub and water closet area now then redo the sink area at another time in the near future keeping the overall plan in mind. Depending on your local real-estate market and how long you wish to stay in this home, your roi will vary. Usually baths and kitchen help with resale value as long as it is an improvement and not a patch job that doesn't update the home...good luck!

I think that the tile in the bath/shower is pretty inoffensive, actually, and would be worth keeping. However, if you have plans to remake entirely, then I'd remake the outer part of the room to match your eventual vision, rather than having to redo it twice. If you think that eventually you might tear everything out, then you might wait and do that all at once -- honestly, I think your current layout would not be superpopular at the point of resale, and you might get more from a redesign that allows, say, a double vanity or otherwise better use of the space.

Updating a bathroom gives a good ROI, but only if you're renovating it in lines with current tastes. From your decriptions, I can't really tell.