Mesa Boogies roots and legacy are in the Mark series.
When Randall started out modding and hotrodding Fender amps, then created the first cascading gain preamps, it was the Mark I. The Mark II/B/C/+ were then iterations and improvements, with the C+ really becoming a company defining amp and holy grail of tone. The IIIs and IVs and now Mark V continue that line by adding more features and versatility to what is essentially still that Mark IIC+ design for the lead channel. The Mark series is to many people Mesa's legacy and their defining sound.
And it's a very different sound and feel than the "other side" of Mesa which became huge and well known, which is the Rectifier line (More accurately, the Dual Rectifier Solo Head, as they had a number of "Dual Rectifier" amps originally which were all very different until the Solo did so well that it became an entire line all it's own).
Obviously they've got some of their British infused offerings (Stiletto, TransAtlantic, etc), Some cleaner offerings (Lone Star), acoustic, bass, etc
But the two sides of the Mesa Boogie coin, the two core product lines that define them to most people, are their classic Mark series amps, and the more modern Rectifier line.
So I think they're just saying "Hey, we did the Mark V, and the 25 and 35 watt versions, and the JP-2C, it's time we heard something from the other half of the Mesa tone legacy. After all those Mark offerings, he's something new that's a little more in the Rectifier vein."
Or they just meant "Something new" the same way that the Rectifier was born from the side of Mesa that is constantly experimenting with something totally new instead of just iterating and improving on a classic old design (as the Mark series is very well locked into the tone and design honed by the IIC+ amps.)