I think it's all but certain that we've reached maximum skyline height, at least for the foreseeable future. There simply is no demand for a new 400 - 500 ft+ tower, nor will there be in our lifetimes -- and very likely won't exist for several generations.
But in no sense is that a dire prospect. We should be thankful for the height that we do have (400-500 ft), which is completely respectable for a mid-size city like Bham. We're taller than anything in Memphis, Salt Lake City, Honolulu, on par with Phoenix, and are marginally outside of the realms of Baltimore and (to a lesser extent) Portland. What we can expect and should be excited about are various high-rise (150-250 ft) infill projects. If we're not going taller, then the aesthetics of our cityscape will be best served going forward by increasing density, and doing so with modern, glass-intensive architecture.
Vesta and the apartment high-rise slated for The Break lot will dramatically change the look and feel of 5 Points. You'd have to guess that Midtown's best bet in landing a new high-rise will be a UAB project. Imagine what that could look like for Parkside / Medical District. Should a developer ever finger downtown for a high-rise project, the ideal location would be one which fills the gap between City Federal and the CBD cluster, giving the skyline almost complete continuity from AL Power to BBVA.
Beyond the feasibility argument, I believe that high-rise infill will do more to complement the cityscape than a new tower would anyway. With 5 Points taken care of, I can narrow the wish list down to Parkside, UAB / Med Dist., or downtown. I think it's probable that by 2028, one of those areas gets the next Vesta-esque project, and it'll look incredible. Icing on the cake would be a new high-rise in Highland Park, but I digress.
Really hate that none of the original designs for the Fed. Reserve redevelopment materialized. We were so very close. That would've already moved the needle nicely: