So the cat is out the bag and I can speak a bit more freely about the Priolite MBX500HS Ultra. There's a promotional video in the link attached.
https://www.kickstarter.com/projects/priolite/priolite-ultra-1-8000th-flash-sync-compact-li-ion
For a limited time early adopters can purchase the lights for a significant discount through Kickstarter. Currently the lowest priced package is running about the same as the 300ws MBX-HS versions.
Key differences with the MBX500HS Ultra are the following.
A) Significantly smaller in size and lighter in weight due to updated internal electronics. I've been speaking with one of the testers and he stated that two Ultras could probably fit in a backpack.
B) Improved battery life due to updated Li-Ion battery (final specs aren't completed yet as they're still optimizing)
C) Improved pricing for early adopters. For reference you could get two lights for less than the cost of one Profoto B1.
The lights are still compatible with the same accessories due to the universal mount. The lights are still universally compatible with all universal or brand specific RC/RC-HS controllers. The lights will still seamlessly integrate with existing Priolite strobes.
***Full disclosure I'm a Priolite Brand Ambassador but I would never promote anything I don't use and/or wouldn't own myself.
Rather than bash other competing products, I choose to speak to the merits of the Priolite system as I feel it can stand on it's own merits without any caveat. There are some different ways various companies choose to go about solving the same problems. Priolite's method works best for what I shoot. It's the only monolight on the market that I'm aware of that allows you to sync at any shutter speed available on your Canon, Nikon, Sony, or Pentax camera of choice and at any power level available up to 1000ws. It is also the only monolight with power options up to 1000ws I'm aware of that provides a user swappable Li-ion battery that allows one to shoot on location or plugged into a wall outlet like a traditional studio strobe out the box without need to purchase additional kits.***