As far as further development, residential or otherwise, I think the next step in a continuing renaissance for Birmingham is going to be the development and mobilizing of a youth culture.
Consider for a moment all the most booming cities in the country right now... Portland, Seattle, Austin, Atlanta, Houston and Denver are a few that come to mind. Young people (like myself) want to be in these places because they have affordable living but also a "scene" ... trendy restaurants and nightlife, cheap warehouses and lofts for creating art and manufacturing locally, tech-friendly everything, etc. Like most revolutions, it's gotta start from the ground up.
Birmingham already has a trump card with UAB (case study: UT in Austin). There's some youth that can create the scene... then the scene draws more youth, then the youth need places to live, then apartment towers go up, then the young residents of these apartments want to forsake their cars and lengthy commute, then the booming tech, medical and finance companies want to be close to the youth to draw the talent, then the companies scout vacant downtown sites, and then they build signature LEED starchitect office towers. It's the circle of life
Cultivate the scene, and the snowball starts to roll.