My own decision with this same mid-2011 i7 ( which runs great with an SSD ) is to wait for Intel's tock release( Skylake ). Even if Apple produces a Broadwell iMac, in my opinion the tock release versus the tick is preferable. Waiting isn't a problem for me, so the next significant improvement( Skylake plus possible upgrades mentioned by other posters ) will make me a buyer. Of course, personal choice and specific needs of each user vary, so YMMV.
Whoever said Skylake was delayed:
http://www.techradar.com/news/computing/pc/unannounced-intel-skylake-cpu-appears-in-mini-pcs-1295466
We'll be hearing more from Computex