The term "Web 2.0" appears to be somewhat encumbered from a "Use it whatever way you want, just like 'GUI' or 'Network' or 'Asynchronous Messaging'" perspective.
Adding a digit, say "Web 2.1" (or should that be "Web 2.1rc1?" is an amusing workaround that has been suggested.
Lying in bed last night (Sleepless in Sligo?) and alternative occured to me. Better to pick a rev number that is irrational (in the mathematical sense). In fact, while not go the whole hog and make it non-algebraic too?
The obvious candidates for such transcendental numbers are PI and E...
And E happens to start with "2.". So we have, "2.1", "2.17", "2.171" etc. to infinity and beyond.
This abbreviates nicely to Web E which is naturally pronounced "Webby" which has a nice ring to it.
TeX users will be familiar with the idea of a version number that asymptotically approaches e as this is what is used in METAFONT.