One of HTC's executives indirectly confirmed that Android 5.1 is likely coming to several Android devices in March. Mo Versi of HTC Tweeted what you see above, stating, "It'll be tied to Google's next MR, which is in March." This was a response to a Twitter follower asking for an ETA on some desired features.
Ultimately, he didn't directly call out Android 5.1, but it's a good bet that Google's next iteration of Lollipop will not be just another 5.0.x version, especially considering we have already seen leaked versions of 5.1 benchmarked in the wild. We'll keep you posted.
Source: Twitter - Mo Versi