@JKMcCloskey Hey James, the HTC One M8 will have a Software Update for Android Version 5.1 and Sense 7 in August 2015 :) HTC UK (@HTC_UK) April 29, 2015
According to HTC's UK Twitter account has revealed that the update will also bring the latest Sense UI. Sense v7 launched with the HTC One M9 and is a relatively minor step forward. One of the welcome improvements is that you can change the grip app switcher to stock Lollipop style. App reshuffling, some new widgets, BlinkFeed updates and other changes are also part of the update.
Other perks like themes were added to the M8 and M7 generation with an update to the BlinkFeed app.