6s 128gb still going strong. Don't see any problem with keeping this phone through 2020 (and 2021 if I have to) even though ios13 will be the last update.
Beyond making calls, iMessage, Safari and Google Maps...I don't need anything else and all that should continue to work past ios13 so I'm absolutely fine. Don't use Apple Pay, financial/banking apps/etc on my phone so my risks will be minimal even when Apple officially drops support,
I figure by 2021, Apple will have added full 5G support and hopefully bumped up to 126gb base. Notch may still be there unfortunately, but if on-glass TouchID is implemented by 2020/2021, I don't see why I won't buy the 2021 iPhone.