I know the epson 3010 supports splitscreen viewing.honestly the only reason i know the epson has it is because i own it. Also it's Not really a feature i care for and the lag on the 3010 is to bad to use it for gaming proposes.
Honestly I do see HDMI being around for awhile but by the time we get affordable 4k video something new will likely take it's place given the current shortcomings of HDMI over longer distances. Just look how hard it is to find a reliable cable to carry a 3D signal. Also I've never seen 4k video and i'm sure i would like it but how much more detail do we need at home. At this point I'm satisfied with what we have and I don't plan on upgrading for awhile. As for 1080p120,...
I also have to say monoprice sells some of the best cables i have ever used i recently ran a 25ft 22 awg hdmi cable. I had to buy port savers because the wire was so thick and well constructed and as for the picture it's crystal clear even when viewing 3D the best part was the cost around $29.00 for the cable.
Using a PS3 I was able to force multichannel audio in the sound settings while using the displayer.the only limitation I've run into is no multichannel audio while watching 3D only 2.1 and you have to switch settings every time you want to watch a non 3D blu ray.
Honestly i've been looking at switching to direct TV for 3D they have about five channels and a satellite feed allows more bandwidth so you get a better picture. Plus getting the satellite is going to costs me the same as i'm paying now for cable the only downside is i have to keep comcast as my internet provider since i can't get fios in my area. So basically it's going to cost me $140.00 a month for both.