It's a fascinating subject and for various reasons I've been living and breathing it for months now.
Evance Wind; my take is that the solution will be found at the radar technology end before the wind turbine. Vestas experimented with radar absorbent paint a couple of years ago however the coating was so heavy it destroyed efficiency and added too much stress to the supporting structures. There has been more headway made with blade design, but given a dream load factor is something like 30%, with the odd wind farm being as low as 10%, it would further degrade that. Also, to change the properties of the wind turbines mid stream in the planning process could materially affect the outcome of the application!
As has been stated above, the race to find a solutions looks set to be won by enhancements to the radar software and hardware. Trouble is, apart from crude RAG (range azimuth gating) and aerial tilting, there's very little that's met with regulatory approval yet, and the fix is expensive. This is detrimental to small wind developments as the developer will usually do a deal with the ANSP (we wont object if you fix our radar) as part of the planning application process.