IO540 is right that very few if any Permit owners are likely to want to spend the money to equip their aircraft to fly IFR in airways, as he does. Most don't hold an IR, for a start.
I think this is a self-fulfilling prophecy. If you're building a kitplane knowing full well that it's not allowed to operate NVFR or IFR, you're going to put the kit in that enables VFR "plus". But if you know that eventually the regulations will change so that you are allowed to fly IFR, then I think you'll find a lot of high-end kitplanes being equipped for that in no time.
On high-end kitplanes, glass panels (a la Dynon) are already standard. A GPS such as a Garmin 496 in a special bracket, or a panel mounted GPS is also standard. Transponder? Can you even buy a non-mode S transponder these days? And even two-axis autopilots, coupled to the GPS, are very common.
Realistically speaking there's not a lot of things you need to add to your average high-end kitplane to make it fully IFR capable. Maybe an ADF, DME and an IFR-approved 430 instead of a 496. When GPS approaches are becoming more common, and when a GPS can be used instead of ADF and/or DME it will become even simpler.