Yeah ... I have an HTC Desire HD, and I'm becoming concerned that it's likely to go down the same path. HTC has issued updates in the past, and may well update to 2.3, but almost certainly no further.
The trouble is that the phone platforms require a lot of porting work, and the phone vendors aren't required to release any of the info required for making Android work on their phones. A giant kernel code drop isn't really all that helpful, especially when it comes without any documentation on the hardware, bootloader, etc.
As a result, Android users are locked in to using the software the phone vendor decides to release. There's no life for the phone beyond what the phone vendor decides to give it - and they're not exactly highly motivated to extend the life of old products.
For me, the other half of the problem is the butchery the vendors perpetrate on Android. It's like buying a Windows laptop from a big OEM, where it's full to the gills with crapware - then being told you can't uninstall the crapware apps, let alone clean-install the system with a stock Windows CD so it actually works.