As long as they keep manufacturing Piledriver-based VIsheru CPUs, there will still be AM3+ boards manufactured.
Now, granted, the Steamroller-based Kaveri APUs are pretty nice: CPU speeds similar to the Phenom II X4s, more L2 cache, & R9 200x series integrated graphics. Those specs compare quite nicely to my current system (970BE with an HD 7450 PCIe card). But they still aren't top-of-the-line, especially compared to the newer "factory overclocked" FX series chips AMD has.
What I suspect is that AMD's plans are to focus on the APUs for "everyday" PC users: the office productivity stations, the non-gamer home desktop user, the "casual" gamer (browser games, low-intensity graphics, "older" games from 3+ years ago that don't even require multi-core CPUs, etc.); they'll compare favorably with Intel's CPUs & integrated graphics, especially price-wise. For the "desktop enthusiasts" & avid/hardcore gamers, the FX series has plenty of life left, especially with the use of discrete graphics cards. And for the happy medium in between, they can always continue their "Athlon X4" series by making Kaveri-based versions without the integrated graphics, using the FM2+ socket.
As for LGA 2011 vs. 1150... Haswell (newest Intel architecture) does not support LGA 2011, so I don't see it being more "future-proof" than LGA 1150. The next step for Haswell ("Broadwell") will, in addition to LGA 1150, support "LGA 2011-3"...except that's apparently a server-only socket for Xeon-series CPUs. And since Skylake (the next step beyond Broadwell), with the switchover to LGA 1151 sockets, won't happen until 2015-2016, you should be good for another 2 years at least.