I think it is more likely than not we will eventually build some taller buildings along the Ohio River toward the West End Bridge. But eventually can take a while to happen.
The pre-renovation Post Gazette building was pretty cool and it would be somewhat bittersweet to see it get entirely demo'ed, but on the other hand you could do a lot with that entire plot.
Here is a nicer image of the planned cap-park over Crosstown:
Part of the appeal of aerial gondolas is they are relatively low-cost and quick to build, and therefore easily scalable too. So you can start with a relatively modest system, and if that proves popular you can then start expanding pretty rapidly.
Still, getting the incredibly clunky U.S. transportation planning and funding system behind even that first modest step is no easy task. But who knows--maybe a new federal transportation bill will happen at some point, and make some room for a project like this.