Dell may have decided not to release a Honeycomb update for the T-Mobile Dell Streak 7, but that doesn't mean an official build for a US 4G version wasn't made.
It was and as luck would have it, it's also been found. The update and package links are below, but before you T-Mobile folk even think about clicking on them, know this: the update will fail on your device.
For some (presumably carrier-related) reason, this build is for an "unknown US" region, which is why trying to install it on a device branded by T-Mobile using the official link will fail.
The good news, for those uninterested in taking the HoneyStreak route, is that it can be manually installed by following the guide put together by Themanii.
And here's the link you should click: xda-developers