OP, nearly same boat as you. I have a 50D. When I got it I had the nifty fifty. Sometime thereafter I got the 85 1.8.
A couple of things about the 85 1.8. I LOOOOOVE it. What a phenomenal lens for the price (or I would argue, what a phenomenal lens, period). It is by far my go-to for portraits. People will tell you it is too long for portraits on a crop body. It is indeed long. But I do 90%+ of my portrait work outside. Too tight? I usually just step back! Pretty easy! In fact I am currently experimenting with my 135L I just got. On a crop it is definitely loooooong, but outdoors it is workable, and it is such a great lens I just want to make it work. That's how I am with the 85 1.8.
In fact, in some portrait session settings I prefer the long length. Sometimes I want the subject(s) to act as if I am just not there (e.g., couples/engagement pics, or kids where I just want them to play with a toy or interact with each other). The longer length lets me stay out of their faces and lets them have an easier time acting natural.
Now, there will indeed be times where the 85 is too long. Indoor portraits could be one, where you want more than just a head and shoulders shot. Also, certain shots outdoors. For instance, in one recent session I took pics of a bro and sis from directly above them with them laying with heads together on the ground, also got above them on a staircase and took shots looking down. 85 was most certainly far too long in both cases there. Thus the nifty fifty is definitely worth keeping for now.
If you do much portrait work, you WILL need a shorter focal length than the 85. But you will also be surprised how much you can make an 85 work on a crop body if you want.
One other thing...I did use the nifty fifty for a long time. Another really great lens for the price. Like someone above said, though, the bokeh could be a little wonky if your background was close behind the subject, or in other instances (like bright spots of light in the background). I recently retired the nifty fifty in favor of a 50 1.4. I have found that much more to my liking for my portrait work. BUT, I really really appreciate what the nifty fifty was able to do for me along the way.
One final thought...unless you are desperately in need of the $$, or unless you have the Mk I nifty fifty with the metal mount, you are really not going to get much at all for it in resale. I think you are far better off to keep it and take the time to save the $90 or whatever small amount you would get for it.