Intel has been changing socket every 2 generations. 1155 is already eol (end of life) with 1150 replacing it. Next gen, broadwell, will be the end of 1150 and skylake will be 1151 which should also be the same for cannonlake. After that it's impossible to tell as info isn't given for things so far in the future. Things can easily change in the tech world so even giving such info is futile.
2011 will stick around a bit longer with haswell-e being on it but with DDR4 coming with hw-e, it probably won't be compatible with past gens. X99 will also get sata-express and should also be used for broadwell-e.
I've always just bought a whole new pc every 5+ years, but with my uses and budget, I typically don't need anything other than a gpu upgrade in between. Any new stuff doesn't matter til I get a new pc. There is never anything that is so groundbreaking that it must be gotten asap. You always just need to buy a pc when you need it and saving on cheaper stuff to later upgrade is a waste of money in the long run. There is never concrete info til close to release time so you can hardly even look to the future.