If you need a brand spankin' new phone, order one or go to the store. If you are asking if you should wait till the next generation this fall, then clearly one does not need, but wants.
My advice if you have to replace a old dying phone is to look for a gently used iPhone 11 Pro or what ever used iPhone you want. I bought a 512GB 11 Pro Max for $900, still under warranty so I bought AC+ for $200 giving me another 2 years of warranty and accidental coverage. Lot cheaper than a new iPhone 12 Pro Max, especially considering the performance of the A14 isn't dramatic over the A13, and 5G doesn't exist where I live, heck I struggle with LTE.
The XS/XS Max is another good value in my opinion, and if I didn't break mine (I replaced the screen, but it didn't look as good as a genuine screen, so I sold it and bought the 11 Pro Max) I'd still be using it and reevaluate when the 2021 iPhone is announced. The speed of the 12 on opening apps isn't a night and day difference compared to the XS, that's why I didn't plan on getting another phone.