When looking into the future it's good to know the past as you can learn a lot for making predictions.
Let's apply this wisdom to the 3G network technology we currently use: I first used HSDPA in a real network back in February 2007 with a HSDPA category 12 Sierrawireless card. At the time, 1.8 MBit/s was the latest and greatest. Since then, networks have been upgraded to category 6, which allows 3.6 MBit/s in theory, and many networks are now category 8 capable with theoretical top speeds of 7.2 MBit/s. Going to 7.2 MBit/s has mostly happened in 2009. But when do you think cat 8 made it to the 3GPP standards? Surely it must have been fairly recently!?
No, not at all, HSDPA category 8 was already specified way back in 2002 in Release 5 of the 3GPP standards. More specifically, category 8 we are using today was first mentioned in V5.1.0 of TS 25.306 of June 2002. That was 6 and a half years ago! These days, 3GPP is working on Release 9…! It looks like that release of the specification was worked on for quite some time as cat 12, which was used for the first devices that came on the market (see above) was only added in V5.2.0 of September 2002 and 3GPP has continued changing the document up until 2009.
I think HSDPA is not an exception but fits a general pattern. From standards to live network, things take around 5 years. UMTS itself is no exception. First specified in Release 99, I got my first 3G phone in December 2004. I was not a bleeding edge user but surely an early adopter. Again, about 5 years from standards to live network.
P.S.: Yes, I know that some operators have announced that they've already deployed HSPA+ with 21 or even 28 MBit/s. In practice however, it's only a couple of base stations in a few select towns.