Why do you want 14 nm for Desktop? What improvements do you expect it to bring compared to Haswell? The lower TDP does not matter much for desktop.
At the same TDP, Broadwell should have a clock speed bump. Intel may choose instead to lower the TDP, but if they don't, 200-300 more MHz isn't unlikely. It should also overclock higher than Haswell. I'm not expecting it to be the next Penryn or anything, but it should be better than Ivy Bridge. Enthusiasts won't have to deal with the regression from solder and planar FEts to paste and FinFETs, so the clock scaling won't be held back. I'm keeping my hopes pretty conservative, though. What I'd like to see and what I expect to see is a return to that magical 5GHz mark that Sandy hit with a good chip, barring unforeseen issues.
Although I'm not counting on it, a 5% IPC bump would actually mean that Broadwell would end up being over 20% faster than Sandy Bridge when overclocked, if it can compete in max-air clocks like I'm predicting. 20% isn't bad at all in this day and age.
Skylake brings more potential for more performance, but it also has more potential to deliver things enthusiasts don't enjoy... wish we knew more about it.