I'm pretty sure replacement engines are still in production for our bikes from Honda, but I'm not sure I'd be interested in paying the price they'd want. There are lots of low-mileage bikes out there that folks buy and don't ride much. I'd humbly recommend looking for one of those garage queens when the time comes. Despite being low-mileage, the values of our bikes drop rather quickly, and the full bike will likely be cheaper than a replacement engine from Mother Honda.

Alternatively, entire engines can be sourced off Ebay from companies scrapping wrecked bikes for really affordable prices, BUT I'm not sure they're 100% reliable regarding existing mileage, etc, so it's a bit of a gamble.

Cheers!