More than surprising: although Samsung someones re-use model numbers I can't find any sign that they've done that with the A50 (there is an A50s, but that came out at the same time so wouldn't account for what you see). And there is nowhere that suggests that the A50 ever had Android 7, and given that it was released in 2019 it would seem incredibly unlikely that it would come with a 2016 operating system (Chinese "fake" phones do that sort of thing, but they never get any updates at all so I think we can rule that possibility out).
Are you absolutely certain that you didn't misread "9" as "7"? I know that sounds almost insulting to ask, but it honestly seems the most likely explanation. Especially since I've never heard of an over the air update skipping multiple Android versions in one go.
As for A11, you are lucky enough that there does seem to be one planned. There's nothing unusual about OEM handsets getting updates many months or even more than a year after a particular Android version is released, assuming they get them at all. If you want the latest version when it comes out then you need to buy a Pixel, otherwise you wait until the manufacturer decides that it's your handset's turn to get the update (updates have to be built and tested for each model, so how long you wait depends on what resources the manufacturer is willing to devote to getting updates out, and for most manufacturers speedy updates aren't a priority).