The real question is: Are there any benefits of upgrading to the new late 2014 mini (compared to previous models) as an HTPC in regards to new video and audio capabilities?
I think the 2011 and 2012 Minis are still powerful and flexible enough to handle HTPC duties for most of us here...I liked that they had both HDMI and Thunderbolt and for me they've always been fairly good bargains because you could put your own 2 drives inside and add your own RAM. After testing a 2012 for a while I went back to the 2011 with the HD 6630M graphics for my living room and have loved it ever since, using both the FW 800 and Thunderbolt for external storage. (I've been a Mac user for a very long time so I was invested in firewire for a long time and I jumped in on Thunderbolt very early, it has been nothing short of amazing.)
I haven't read reports of anyone who has gotten one yet, but I doubt there's any significant difference in audio
with the 2014's, we'll have to wait for an official tear-down but Apple's not gonna change course now and all of a sudden support the high def Bluray audio formats. What I like about the 2014 is they've kept the HDMI and added a 2nd Thunderbolt port (the loss of FW800 is no big deal unless you work with professional audio apps and have firewire interfaces, there has been some discussion that the inexpensive TB to firewire adaptor doesn't do bus power as reliably as native FW ports.) HDMI, two TB and a bunch of USB3 ports will be pretty nice on something so small, reliable and cool-running. I feared Apple would change the form of the Mini and severely reduce its footprint. They did not, so far so good.
But, if as stated the RAM is no longer user-upgradeable, i.e. if it is indeed soldered on AND it's not as easy to get inside to swap drives or add a 2nd drive, then that changes the Mini value equation for me a little bit--you'll be paying Apple to beef up your machine rather than rotating your own stuff inside and shopping for bargain RAM. I'd give at least some consideration to staying with a price-reduced 2012 refurb that you put your own RAM and drive(s) in. Thunderbolt daisy chains quite nicely, and both the 2011 and 2012 Minis boot perfectly off of SSDs in Thunderbolt enclosures if you are the slightest bit concerned about opening the Mini up yourself...because my experience doing this has proven so safe and reliable, I suspect even the low end 2014 Mini with the Intel 5000 at $499, which seems like a weak value proposition on paper, will do quite well in the home theater if you boot it off an SSD over Thunderbolt 2.
That has me thinking, the low end 2014 model may not sell all that well, if it exists mainly to get people to step up to a machine perceived to be a better value at a higher price point, as result it may show up fairly quickly as a refurb and then I may just upgrade to it since I'm already set for external SSDs and Thunderbolt.