Intel typically only uses the same socket for 2 generations. Now that they have abandoned their traditional tick-tock cadence of CPU releases, they may start having 3 gens on 1 socket, but I don't think anybody knows at this point. So no, you will not be able to buy the latest CPU 5 years from now and have it fit in an lga 1151 mobo. At best you could upgrade to Kaby Lake (late this year), or maybe Cannonlake in 2017.
That being said, if you buy a good lga 1151 CPU now, you won't need to upgrade for 5+ years. As far as other mobo features, there'll always be something new around the corner. For example, Intel's next gen mobos have support for upcoming XPoint memory. At some point PCIe 4.0 will be added to mobos. There's always new, higher-bandwidth connectors being released on new mobos, etc, etc. You could spend the rest of your life waiting for the next big thing to come out. But right now lga 1151 is the most future proof you can get.