Yes, the inputs (3) are all HDMI 2.0a. The only point is that the single HDMI output need only be 2.0b to support eARC.
The Sennheiser reply is that the single HDMI output is 2.1. If they implemented 2.1 for the single output, why not implement 2.1 entirely and have a future proof product with that spec? As long as their claims of eARC support are accurate, I guess it does not matter if 2.1 or 2.0b was implemented for the output side. It will work. Cannot wait to grab one!
But if you are right, then why in their own website they write eARC as an HDMI 2.0a ?
The following comment from Sennheiser Technical Support is what I was given. "The HDMI out (to the TV) is HDMI 2.1. That's why we have the eARC functionality." This spec is not mentioned anywhere on their website about the soundbar which is why there is the confusion. Since I plan to connect all of my sources via HDMI direct to the soundbar, the eARC function does not even come into play for me. All I want going to the TV is HDMI video (X3) passing all of the 4k processing and the HDR data. For those wanting or needing eARC, they should be fine.
There is no way on earth that you guys are going to be disappointed with this thing. The design of it, with its quite large drivers, and Sennheiser's technology and expertise is obviously reflected in its early reviews. If I had the money right now, I'd be preordering too.
TV: Samsung Q90R, or LG C9, or Sony ...
Blu-ray: Panasonic UB820, or Sony X800M, or Pioneer Elite LX500
Soundbar: Samsung Q90R, or Sennheiser Ambeo, or...
AVR and Speakers: Marantz 8012, or... and GE Triton Reference, or...