You What you are actually looking at is the leading edge of an S curve. That curve will climb steeply and power up nearly vertically for a while before tailing off. It is not easy to estimate how high this bird will fly but it will be a hell of lot more than 4x. I would think 1000x would be a better estimate!
Well my statistical observations give me about 20% increase - it's pageviews a month for Cyrillic IDNs. It doesn't have to be all the time, but should be about 10x increase a year - this is just an extrapolation :-)
10x per year, but at what point does it level off?
Also, I think this 10x figure may assume steady technology without breakthroughs. IDN-compatible browsers and awareness will cause a sharp increase (hence, the S-curve) and growth in internet penetration will accelerate that curve. At some point, it will level off as internet penetration growth stagnates and IDN-awareness becomes commonplace.
I won't say 100x or 1000x. I will say that I have no idea. But, I do believe that it will jump sharply in 2008 and 2009.
It's always good to be an optimist :-) 
