This 'delay' of rolling out new versions of Android is hardly the fault of Google.. the fault lies primarily with the TelCo's who seem to take their sweet time pushing out the updates... adulterating Android with their 'skins' and associated bloatware... and also, sometimes, it might not be in the best financial interest of the TelCo's to push out the latest Android update.
If they can 'ensnare' customers in new 18 month long contracts on the latest mobile running the latest version of JellyBean - with the latter as a selling point, then why would they feel an incentive to push out that new OTA update for free?
Of course they're not going to do that ... they're going to allow customers to go through the natural upgrade cycle... ie., wait for customers to get bored of their current handsets and inveigle them into a new contract with a nice new shiny 'phone running a nice new shiny version of Android.
And that, people, is the reason why Gingerbread is still the predominant ROM on most peoples 'phones.
------
Of course, with a bit of knowledge and some research, you can screw off that particular business model, and ROOT and FLASH a custom ROM of your own selection.
Rgrds,
SebJ.