I play MS Flightsimulator 2020 on the system in my signature @ 1440p (i9 9900K and RTX 2080 Super), and I use the so called "High End" graphics preset (the step below "Ultra") and live streaming of sattelite data, and in the large airports and in big cities with dense scenery, my FPS dips as low as 34 FPS, and generally peak at just 50-ish FPS. It averages around 40 FPS.
So it is going to be very difficult maintaining 60 FPS at 4K even with the most highend hardware, unless you turn down the graphics settings.
I do use AA though, which you c ould probably do witout at 4K, so at least that will give a minor performance boost.
But as mentioned in one review I read recently (after the release of the game) - MS Flightsimulator usually has a fairly long shelf life, and the hardware to play the game at high FPS and high / ultra graphics settings, probably isn't actually available on the market yet.
I'm personally very curious to see how well the upcoming Nvidia and AMD graphics cards perform in MS FS 2020 once they hit the market
But I personally think that 4K 60 FPS is not something you'll see for a while.
EDIT :
I'd recommend installing the game on an SSD, as it has some quite significant load times. I initialy installed the game on a SATA3 2.5" SSD, but quickly moved it to one of my NVMe drives instead. Installing it on a mechanical HDD would require some patience at certain points.