A few concerned members of XDA forums contacted HTC and asked them whether or not the Sensation 4G would eventually be unlocked for bootloading. Here is HTC's response:
We are currently developing new bootloader unlocked software for your phone. HTC is still committed to allowing our customers to unlock the bootloaders if they wish, however we are still implementing the policy and many updates were already finalized prior to our change in policy. We apologize for the inconvenience, but be assured that we are working on a solution for our customers and our commitment has not changed. Please stay tuned to our official channels for ongoing updates on how we will be implementing this policy.
This is good news for prospective HTC Sensation owners(Release date of June 15th on T-Mobile), although HTC does need to notify customers which previous device models will receive the update and when the update will be issued. Hopefully the update will be issued not to long after the Sensation's release. It's nice to see HTC keeping to its promise and attempting to please device owners.
source: Unwired View