The performance difference is somewhat small between Ivy Bridge and Haswell. On average it is 6% assuming the same clockspeed. Socket 1155 is basically dead since no new CPUs will be released. As for socket 1150, there is expected to be a refresh of the Haswell core next year. Intel was originally going to release Broadwell in 2014, but it seems they are destined to be embedded into motherboards and sold to OEMs, not consumers. Not sure what the refresh of Haswell means for performance. I would expect any performance increases to be rather small. Perhaps just 6% again, but who knows...
From an upgrade standpoint, there is no upgrade if you buy the Ivy Bridge i5-3670k except maybe to the i7-3770k, but most people do not need to use Hyper Threading. Getting a Haswell CPU will potentially give you the opportunity to upgrade to a "Haswell Refresh", but the perform gain will probably not justisfy spending more money on another socket 1150 CPU.
Skylake is expected to be released in 2015 and it is expected (or hoped) that with Skylake Intel will go back to double digit (% wise) performance increases.