The Galaxy S10 series may have already started receiving Android 10 in some regions, but Galaxy Fold owners are not so fortunate. One UI 2.0 roadmaps state that the device still has another four months to wait before it sees an OS upgrade, despite being Samsung's most expensive smartphone. The Galaxy S8, S8+ and Note 8 are unlikely ever to see Android 10, either.
https://www.notebookcheck.net/Samsung-snubs-the-Galaxy-Fold-while-dropping-the-Galaxy-S8-S8-and-Note-8.445046.0.html
It took them only 2 years to cut support for their once-flagship phone. I hope I'm never stupid enough to buy from this company again.
Unfortunately 2 years is the normal cut-off for OS updates support with most Android manufacturers, including Google. If you want longer, get a phone with good support on LineageOS (such as OnePlus, Motorola or Pixel) then go that route when official support stops.
Or get an iPhone and enjoy at least 5 years' support?