When will there be a new version of varia radar 515?

What new feature are you waiting for? The 515 works really well, battery has decent life. Can't think where they'll improve it tbh, apart from reducing the price maybe. 

Well, It is a good question. Garmin is usually updating products every 2 years, and FCC requests for their radars are matching this pattern, but I am afraid that they already released their new radar - a wired version of radar - Cannondale SmartSense www.cannondale.com/.../what-is-smartsense

I would expect usb-c input at least...

For me would be usb-c and a quicker charging a really good reason for upgrade :)

Ok, the expensive part of this cannondale combination is the bike

My wish list would be:

1. Lighter, whilst still having the same radar performance, brightness and battery life
2. A red reflector on the rear face, to save more weight by not needing a separate reflector to comply with the law
3. USB-C

I doubt these changes will happen soon so go with the current version. I've still go the 510 and see no reason to upgrade to the 515. 

I want integrated safety video camera functionality like that offered by Cycliq.   I’ve used my Varia in conjunction with a Cyclic Fly12 CE (front) and Fly 6 CE.   But the Cycliq products are garbage and the customer service is dreadful, at least in the US. 

I’m thinking about now purchasing a Varia front light to use in place of the Fly12CE, primarily for daytime use. If Garmin can integrate video cameras into its Varia devices,  it will have winners.  

Looks like Specialized is also using the same wired radar unit on their current Vado 5.0 and Como 5.0 e-bikes.

I have not had a good experience with the Varia or Garmin: I purchased two Garmin Vario RTL 515s from Bike tires Direct approximately 16 months ago. My spouse's unit will not take a charge after using it a maybe 10 times. I called Garmin and they refused to do anything for me because "the one year warranty has lapsed" other than to let us purchase a "reconditioned" unit for half price with the unit having a 90 day warranty. Now why would I pay ANYTHING to Garmin for a unit with a 90 day warranty, after having a virtually brand new unit go bad after 10 uses? More precisely: Why would I pay Garmin to screw me a second time?

EDIT: Within 10 minutes of posting I got a message from Garmin claiming that my comment was SPAM, and was slated to be removed. Clearly a Garmin employee is tasked to keep complaints off of this site. Bui what else would I expect from this company? 

I would wait for a very long time. Do you mean a product that lasts longer than 10 uses? I purchased 2 approximately 15 months ago and my wife’s unit failed after being used 10 times, which  is not an uncommon experience apparently. Garmin refused to replace the unit because it was outside of their worthless 1 year warranty. Bad build quality!