The new engine is just that - NEW. Polaris built (or had it built to their specs) for the Slingshot. I'm sure they have put it through the "usual" testing, but to say they have results of hundreds of thousands of miles and years of use is not what you'll hear about this engine. I'm sure any issues with it will occur in the first two years of life and the warranty will cover it. I would not hesitate about buying one if I was in the market for a new slingshot. If you're looking for a reason NOT to buy ANYTHING, you can find several reasons from any product. Buy one, ride the hell out of it, and enjoy it.
This caused me to recall all the issues that arose when the SlingShot was first introduced, oh the whining, crying, bitching and complaining that went on because of it! But Polaris handled these issues each one by one and ultimately the SlingShot become a pretty dependable machine. I would have confidence that Polaris will continue to do the same with the 2020 and following generations.
Bill
This mirrors my belief. This engine is new but the Polaris engineers didn't start with this engine. They have lots of experience to draw on. My expectation is that there will a couple, three hitches that need to be tweaked and that within a few months they'll have a solid platform. I may not be a buyer but, hey, I got mine!