Depends on your needs
The big changes were always expected in 2020...for me i’m Upgrading as i badly wanted a great camera with night mode...it has better battery life and likely better Face ID with slightly better screen quailty...
For a lot these aren’t needs but for me i will take it. I upgrade every year so for me it’s worth it but for many on a Xs it isn’t.
Wait til next year for those who aren’t happy. That will be where we will see good improvements.
Unless you’re tied into Apple’s ecosystem, or you’ve got other compelling reasons to remain on iOS (for me it’s the Mail experience, not on iOS 13, but generally), there are several other options that offer an amazing camera experience. Remains to be seen how good the new phones are in the camera department, but if price is a consideration, I’d definitely look at Android phones.
Your point re 2020 iPhones may be valid - it may be a bigger upgrade in terms of design and new features (e.g., 5G support), but then I can bet they will also increase the price, so the value proposition will likely suffer.
That being said, all things considered, I think this year’s iPhones are a decent iterative upgrade, but as a customer I can’t help feeling shortchanged with the 64 GB base variant.