I think the mass market excitement for HTPCs is gone. Through a combination of alternative solutions (cheap streamers, smart TVs and Blu Ray players with better compatibility), the lack of progress of the WMC environment (software, remotes, etc), and the advent of tablets and smart phones, it has become a niche market. DRM also remains a major issue.
On the positive side, what we have today works failry well (I remember the days of trying to get DVDs and then HDTV tuners to work on HTPCs). There is no need for cutting edge hardware for most applications.
HTPCs remain the best solution for niche uses (calibrated 3Dluts/and quality upscaling for video projectors and the like, using solutions such as Madvr, at great price and with improving results), but this is a very small market. Interest for 3D has been limited and is now nearly gone, and I'm not sure how 4K will fare.
In terms of exciting new developments, Media Browser (with MadVR, etc.) seems to be the main game in town (It's great, but there is less activity than in the old days of Meedio, WMC, ffdshow, Girder, XBMC, extenders, etc.). I also guess that the old timers have moved on to new hobbies and family occupations, while the younger generations are more into laptops and portable technology.