I'm actually surprised that Wimberley's MonoGimbal concept hasn't hit the market at least a decade ago with so many bird/wildlife/sports photographers using monopods out in the field. I suppose the reason for that is simply because so many haven't been sold on the idea of a need for a Gimbal head on their monopods as much as on their tripods.
I for one am a huge fan of having a Gimbal head on my monopod, so I've been using the Sirui L-20s (with RRS Lever QR plate) with a great satisfaction. If I had known about the MonoGimbal by Wimberley at the time of shopping around, I'd have gone that route instead of the Sirui's. The main difference between Wimberley's MonoGimbal and Sirui L-20s-as-Gimbal, however, is the free weight balancing with the Wimberley's whereas with the Sirui's your hands cannot entirely be freed without having to tighten the knob first. This minor inconvenience hasn't bothered me a bit and certainly not enough reason for me to replace the Sirui with the MonoGimbal, especially when I'm not a big fan of Wimberley products to begin with.
A few days ago I sent an email to Wimberley with the question as to whether they're planning on coming up with v.2 of MonoGimbal, and the answer that I received today was no. As a big fan of ProMediaGear, I then sent an email to request that they come up with their own version of the same if they aren't currently in the process of making one already. It'd be interesting to hear what they have to say about this or whether some other Gimbal producing companies would follow suit in the near future.