Only time will tell how quickly updates will roll out for the One. Updates for any Android device (excluding the Nexus series sold directly from Google which run a stock version of Android) take more time than an update to iOS. Each manufacturer has to roll their own customizations into the stock version, then it has to be sent to the carriers for testing and their own additions, and finally rolled out to the devices that each manufacturer and carrier have chosen to get the update.
Since the One is currently HTC's flagship Android device, it will almost certainly get updated to 4.2.2 at some point, hopefully in the not too distant future ... or possibly skip 4.2.2 and go straight to 4.3, or whatever version is set to be announced at the upcoming Google I/O event. It sounds like 5.0 Key Lime Pie is still a ways off (still in development) and we will be seeing Jelly Bean 4.3 before 5.0 is released, so it really depends on how far off Key Lime Pie really is. More than likely, the One will get 5.0 at some point after it's eventual release, but when is really anyone's guess.