HTC just sent out this very cryptic image to members of the press. The text of the email doesn't offer any further clues, simply stating the company "wanted to share the date of our next big announcement."
Even more puzzling is that HTC's announcement comes after the 2017 Consumer Electronics Show, a stage where companies typically make product and partnership announcements. However, HTC has made its last few announcements online, instead of hosting extravagant and expensive events with HTC executives and members of the press.
"For U" is the only clue, and not a big one at that. However, HTC does have a history of partnering with fitness brand UnderArmor to produce wearables. Perhaps, we will see another fitness band or smartwatch? It's a bit early to see an HTC 10 successor, but anything is possible.