Millions of people ascend to the height of Everest's summit every day, extremely quickly. I imagine that such a purpose-built gondola would, like modern jets, have a pressurized cabin.
What makes the top of Everest interesting to visit is that to do it, a person has to overcome very difficult natural challenges. So a gondola to the top would destroy the very value it was supposed to provide.
It's not some trivial walk around the park just because it's not considered one of the hardest summits in the world.
As for whether or not the gondola would be a good thing, I guess that'd depend on a lot of feasibility studies and cost analysis (cost to the environment, to the local populations way of life, monetary costs).
Millions of people travel in commercial airliners every day, at altitudes greater than the summit of Everest.