Check out the link below to access a good article on bathroom remodels. Don't miss the first link within the article, "Cost vs. Value", which will take you to a table that shows the return percentage for various home upgrades. However, be careful, these percentages are averages and may not represent what the remodeled bath will bring when your particular home sells.
I find buyers less interested in jetted tubs than they were a few years ago. It's possible that reports about bacteria collecting in jets put people off of those a bit. Soaking tubs are a big deal to most people, however. If you're able to do a separate shower, that appeals to most of the buyers I am working with.
Also, one of the most important things you can do is also one of the most cost-effective. Use an attractive, neutral paint color on the bathroom...no wallpaper.
I would advise against getting rid of Bedroom 4. More bedrooms gives you a chance at attracting a wider pool of buyers.
Don't hesitate to ask if you have additional questions about your real estate needs. I'll be happy to give my thoughts or come by to give you a price opinion on your existing home.
All the best...--Nancy