Following the European Sensation and this morning's EVO 3D's updates to Android 2.3.4, which, among other things, brought bootloader unlocking capabilities to both devices, T-Mobile just announced that the Sensation 4G is now receiving the 2.3.4 update as well. The update (software version 1.45.531.1) brings the following changes to the device:

The update to Android 2.3.4 / software version 1.45.531.1 has the following features and improvements.

New Features

    • Software stability
    • Improved battery life

Improvements

    • Improvements to Trace dictionary
    • Improvements to screen responsiveness
    • Improvements to video playback
    • Improvements  regarding device reboot / power off
    • Improvements to icon  pixilation
    • Improvements to Wi-Fi connection
    • Improvements to screen/photo resolution

I'm willing to bet that the update also brings bootloader unlocking, just as soon as HTC opens up the flood gates over at HTCDev.com's bootloader unlock page.

To check for the OTA, go to your Settings > About screen and tap HTC software updates. Note, however, that the update will be rolling out in stages and can go well into September, according to T-Mobile:

The update will continue over the following weeks and not be complete until late September.

We cannot expedite how  quickly you receive the update.

Source: T-Mobile via @T-Mobile