First, the 970 can switch HDMI video via the DVI ports. You will still want to use the multichannel analog connection of course, but you can switch two HDMI sources to one input in your TV. My setup guide describes all of that.
Since neither the 997 nor the Emotiva are here yet, it's impossible to accurately predict sound quality. I will say that the BDP-83 compared extremely favorably to the Onkyo 885 (multichannel analog vs. HDMI with Audyssey), making me suspect that the big question is about how well Trinnov works out. If it can offer something Audyssey can't (and that's exactly what Trinnov and Sherwood are suggesting), there is an opportunity for the 997 to do what the 885 didn't: offer a clear and decisive advantage via HDMI compared to analog. The 885 is a damn fine piece of gear - I don't see the Emotiva offering better, and Trinnov us really the biggest difference between what the 997 will offer and what the 885 offers. If we extrapolate from that, I could see a 970/BDP-83 pairing offering something easily on par with an Emotiva/BDP-83 combo. A 997/BDP-83 combo may offer something extra, but you will also pay more to get it.
Remember - all of the above is one guy's theorizing without first-hand experience...