UPDATE 7/25: After only a few days, the petition asking HTC to release a stock Android 4.0 build for the HTC Desire HD has already recevied over 10,000 signatures. If you have not already A while back signed your name to the petition, click on the link and help support those who still own and use the HTC Desire HD.
HTC stated that they would be updating the Desire HD device to Ice Cream Sandwich.  However, it looks like that is no longer the case.  HTC has changed it’s mind and will not be bringing Android 4.0 over the Desire HD stating:
After extensive testing, we’ve determined that the current version of HTC Sense with Android provides customers with the best experience on the HTC Desire HD. When we consider new versions of software, we weigh a number of factors, but ultimately the customer experience on the product is the deciding factor. We apologize for any confusion this change may have caused our customers.
Fortunately, all hope is not lost.  XDA Senior Member max63094 has taken it upon himself to start a petition to bring ICS to the Desire HD.  The goal is to bring Ice Cream Sandwich to the device even if ported without HTC’s proprietary Sense software.  The original HTC Desire received a similar build when a Gingerbread RUU without Sense was made available for the device.  The recent ICS ROMs created by developers demonstrate that the Desire HD can run ICS without issue and have worded the petition to reflect this knowledge:
Now anyone over at XDA knows this is not true, ICS runs great on our phone plus it is also a better experience. Now this petition is to get HTC to release ICS for us, if they do not want to give us Sense, then they could do at least what they did for the HTC Desire, and release a pure Android on the HTCDev.com With the HTC Desire, they released a RUU because the phone could not handle sense with gingerbread, so they released a pure Android, and now they need to AT
LEAST do that for the Desire HD with ICS.
The community support for the Ice Cream Sandwich is amazing as the petition has received almost 4 times the goal of 2000 signatures.  You can find more information on the petition on the XDA Forum thread here. When you are ready to sign the petition indicating your support you can visit the site here.
Keep in mind you don’t have to own an HTC Desire HD to sign the petition.  Head over now to show your support!
Source: XDA Developers