This depends on the buyers personal preference but in general this arrangement should be satisfactory for most families.
Adding an additional bathroom upstairs may not be an easy fix because it will depend on the location of your water and sewer lines. To add another BR may force you to decrease the number of bedrooms as well.
Hope this information is helpful.
The "Eckler Team"
It will also be very nice to have a bedroom and one full bath downstairs - for guests, especially with aging baby boomers where we have elderly parents to take care of; or even if we are looking at our own future.
Adding a bathroom is generally pretty big task to take on. You have to first see if there is enough room in a logical location for the bathroom without sacrificing other amenities upstairs. Then the bathroom itself is difficult to do - sink, tub, faucets, toilet., etc. Not an easy task.
Maybe you can get a contractor to come out and give you very rough idea about if it is even feasible.
A minimum of 2.5 baths with 4 br's is good. It would be better to have an add'l bath on the 2nd floor. It will depend on how many people will be living in the home. If when you resale you sell it to a family with one child, perhaps, then they use the other 2 rooms for an office and the other for a work out room or something of the like, then you should be good. We do have someone we're working with right now who's facing the same thing you're talking about and there are many homes in their price range with the add'l bath up.
Happy to help,
The Hayley Group - Keller Williams