Except if you really need the money you should keep it. You already said you had fun with emulation and a few exclusives on it. I'd say you'll regret it if you want to play another exclusive or a favorite emulated game and you don't have it anymore.
I don't know why you want a Switch but I hope that you know precisely what you are going to get with it. Better lower your expectations, on a technical point of view. For the same price, Series S is a million time better, unless you are planning to play handheld. In this case, a Switch Lite is much better suited, even though ambitious games still look and run like poop on it (that's the same on OLED/normal Switch of course). Smaller screen helps mitigating the issue, but does not miracles.
If you already have a Switch, upgrading is utterly pointless. Just my two cents.
Well, I ultimately decided against the Switch. I had both a OG Switch and a Switch Lite and just didn’t care for them, so I doubt that would have changed with OLED. I just ordered an Xbox Series S from Amazon for delivery this Saturday. I think it was a good move to make.
EDIT: I ultimately cancelled the order for the XSS. I figure I can just wait out the next 30 days and then get either an XSX or a PS5. That is a much better investment IMHO. While I could have gotten right into gaming with the XSS instead of waiting, I’m sick of selling stuff and packing/shipping it. I don’t want to bother with that crap anymore.