The Mummy is my favorite ride at the Studios. It's got really cool scenes and effects, some awesome AAs for Uni standards, and some nice airtime at the beginning. It's not perfect, but I still love it. If UOR decided to get rid of it, I would not be happy.
The USH version has a better story than USF's "We're going into the movie" narrative, but it is really doesn't bother me that much. If they wanted to make improvements on the story, It can be an easy fix. Just get rid of any references to it being a movie set in the queue. The facade can stay disguised as a meuseum and I would still buy the transition into a cursed tomb.
Other than story, I think the only glaring issues are the turntable room and the ending. Put some stuff in there and switch out the transition scene of lit up writings on the wall for USH's zombie room and it would be a perfect ride.
The Mummy shouldn't close since it's my favorite indoor coaster ever. If anything make improvements. Since the new one isn't doing so hot (But doing pretty good overseas, oddly enough), I'm glad this won't be going anywhere. I guess it would cancel out any hopes on improving it though.