Mint 4.0 KDE Edition should be out soon, too soon to include KDE4. But there is always Mint 5 KDE, which should be out in about 6 months, by which time the KDE guys will of had time to squash some of the bugs (KDE4 is supposed to be very buggy at the moment)
In fact, you aren't really missing out on anything, because I don't think KDE4 will be widely adopted by any Distros for 6 months anyways.
It does look sweet, but it seems a massive amount of degguging still remains before it's ready to use without driving you up the walls... So if we can have it in Mint 5, it probably be a lot smoother...
I don't have a solution, but I do admire the problem.