With Sony Ericsson's recent announcement that they will be upgrading their existing Xperia lineup to support the latest Ice Cream Sandwich or Android 4.0 OS from Google, HTC has been pretty quiet about it and has just officially announced that ICS will indeed be coming to "as many HTC devices as possible".
Our best guess and bet is that HTC would (and should) upgrade their latest lineup of products first, especially those that were released this year, then followed by the ones from the previous year(s) and so on. Don't expect it to come anytime soon yet, this is just news to whet your appetite. With ICS, HTC now has the chance to start fresh by deciding whether to still bundle their Sense UI to the OS or leave it stock (with perhaps some minor modifications).
Leaving the OS mostly stock is a better choice which will reduce the turnaround time when a new update of the Android OS comes in. But I'm sure this will not be an easy decision either because doing so, may make customers who love and are so accustomed to their Sense UI to feel a bit "empty" with a stock Android (even though the stock ICS is pretty good on its own without any custom UI or features already).
This is something HTC must decide or better yet - ask the customers themselves, make a poll, survey. Obviously the best way to do this is to have an option to have either Sense UI or a stock experience, but the problem would be delivering the updates to the end user - they have to choose either one for the OTA updates. Alternatively, they could put up the Sense UI with the OTA updates to please the general crowd and for those who wants the "stock experience" can go ahead and grab a separate update file (for power users) from their HTC developer channel.
Sounds like a good idea right? Well, again this depends on the quietly brilliant company. Lets wait and see how this plays out.