The current AM3+ flagship line up is Piledriver.
Unless you've simply not got the budget for an 1150 system with an i5, then buying into AM3+ now isn't the best of idea's.
AM3+ looks like it'll be replaced in 2016, but AMD look like they're still bringing out new APU's with their new iterations (Steamroller for example is out as an APU, but not as an 8 core flagship chip)
There's no sense in this though, Intel sockets have less longevity than AM3(+) has had, typically 1-2 years. No such thing as "future proof" in this sector.
Don't think you're being very objective at all there.
AM3+ as a platform is outdated, it has a lower performance potential. Having an ancient platform that's outdated but not yet replaced doesn't mean it has a higher longevity than Intel platforms which have modern features and a higher performance potential.
Socket 1155 came out before AM3+, yet has PCI-E 3.0 and a higher performance potential, please tell me how the AM3+ has more longevity?
Socket 1150 may not have the same longevity as 1155 before it comes irrelevant as the performance potential hasn't gone up much despite the 2 year gap, but it's still got an even higher performance potential than any of the AMD set ups.
Also, if we actually delve into history, take socket 1366, that came out more than half a decade ago. AM3 came out after, but guess which platform is starting to offer performance that people find is too low? Yeah, the AM3 platform. The 1366 socket had a higher longevity by far as the performance it offered and still offers is higher than that of AM3. Ignoring how AM3 actually had no exclusive CPU's and was basically a waste of time socket, and the very sketchy way AM3+ was handled.
TLDR : The sockets which offer the highest performance potential are those with the higher longevity, and that would be Intel, not AMD.