There is no official confirmation on this one, so view it as a pleasant possibility; supposedly HTC is currently considering options to allow current HTC One owners to trade their Sense 5 in for a vanilla Android ROM. Apparently, HTC has listened to its customers and their valid concerns that it seems unfair they will not have the option because they were early adopters. Here's a quote,
If this rumor is true it's pretty amazing to see HTC bend over backwards to please their customers.HTC also provided another interesting tidbit: it's currently "examining the best way to support early adopters of the One" that may prefer the stock Android experience over Sense, perhaps by way of an AOSP ROM. The company isn't providing specifics on that front just yet. Still, if you're a One owner feeling burned by today's announcement, there may be hope.
Source: The Verge