Well Piledriver is Bulldozer with a bunch of fixes. The next few uArchs from AMD will most likely be Bulldozer + improvements as well, since its AMD's first major rework of their uArch since K8. Bulldozer itself isn't a bad idea, execution was severely lacking though. Trinity shows that its 15% improvement on performance per clock per core over Bulldozer I think.
Technical stuff about changes from BD to PD if interested
here.