There's far more to AM3+ CPUs than meets the eye. Most namely, they have all of the instructions needed to run Virtual Machines without needing to run a locked I7 (K series usually have it all disabled).
The Core I3 6100, even unlocked, still can't catch the 8320 @ 4/6ghz in heavily threaded apps.
Whether or not that makes it worth doing now? no idea really. I guess they are still seeing sales or they wouldn't bother. Only problem is if the I3 6100 really is unlocked (and it's looking more and more likely) then many will choose it for the better gaming performance.
Mind you, if the market for AM3+ is in Vmware and so on then that won't touch sales any way.