I'll just throw a "what-if" out there...
What if Smith and co. are really over the Mark series. Really, think about it...Mesa has been moving in other directions. Yes, the Mark IV is a great amp, but the company has been developing a lot of other amps in the meantime. The Mark has been a great cash cow and totem for the company, but times are changing. I'm not talking about the following the Mark series has, I'm just looking at where Mesa is putting their time and effort. The LSS, Roadster, Stiletto...I think they're moving away from the Mark altogether. Read interviews where Smith goes on and on about Class A...is he talking about simulclass? Nope, just pure Class A. He seems more excited about the simple things these days.
Now I'll also say that Mesa has come out with some wild complicated amps with the Roadster and Road King, but really, stuffing 4 amps in one box really isn't that complicated. Each channel is it's own amp, if that makes any sense. I needed a slide-rule to even attempt to dial in a Mark. If a Mark V hits, I'd expect it to be a VERY scaled down, high gain amp. Three channels at the most, and I would say that would be pushing it. What would be the best move for Mesa? Maybe a single channel, high-gain amplifier with a 5 band EQ with a smaller price tag? If they priced it in the range of the single rectifier, I think they'd make a killing and end up with an even larger following and a wider customer base to unleash a more "complicated" mark in about 5-10 years.