However, it looks like HTC has changed its mind and has decided to update the U11 to Bluetooth 5.0 in the not so distant future. According to FCC (Federal Communications Commission) filing, HTC plans to “enable Bluetooth 5.0 by software without any hardware change.”
With Bluetooth 5.0, HTC U11 will have longer connectivity range, as well as higher transmission bandwidth and lower power usage. The upgrade will be made via software update, which should be marked by HTC in the changelog.
Sadly, it's unclear when exactly the new update will be released, but if you own the HTC U11, you can be sure your phone will make use of Bluetooth 5.0 if nothing wrong happens.