I love my RA, but I can see why they cancelled it.
Mesa's already got several Swiss Army knife amps, and the RA doesn't look like one from the front but it's actually complicated as ****. The RA's big selling point was Multi-Soak, which I don't think they ever really got around to explaining how to use - there's a reason there's one for each channel, and that's the reason the amp's so complex. You can't dial in a sound and then just use Multi-Soak like a master volume. They're volume controls, sure, but more importantly they are tone controls. And I think a lot of players don't understand that you just can't get the "loud" sound without blowing some air through a good cab and some speakers. Hi on the RA with the soak up all the way sounds good through a little 1x12, and I have had many a pleasant evening of wailing with a doobie and just that setup, but it doesn't sound or record like a Loud Amp.
As well, the reverb and fx loop just didn't work as well as they should on a big-name amp in the 21st century, and there's a switch for 6L6 but I never got the amp to sound anything besides awful with them. Since Mesa's perfectly capable of making good reverbs and fx loops and multi-tube power sections, I am guessing that there's challenges from Multi-Soak that they can't fix without compromising something else. I personally would be perfectly happy not even having any of these options, but it would lessen the curb appeal for a lot of guys.
I really like the sounds I get out of mine but I'm not sure I'd pay full price for it (IIRC I was at $2300 Canadian all in, I bought the first one in Ontario or Quebec for sure and probably the first one in Canada) again. Helluva bargain at $1200, though.