We are going to upgrade one of our SDL Tridion implementation from 2013 SP1 to Web 8.5. We are using DD4T 1.3 with in-process while for the upgrade we are planning to use CIL. We are considering DD4T 2.2 for the upgrade but want to understand if there is any benefit\challenge we are going to have if we use DXA instead of DD4T so that it will be future proof considering merging of DD4T and DXA.
To learn more about the merge and DXA benefits and How it affects you, you can check out the following blog posts:
DXA 2.0 AND DD4T - dd4t.org
Merging DD4T and DXA - Bart Koopman
DXA 2.0 architecture - Bart Koopman
How Will the DD4T and SDL DXA Merger Affect You? - Chris Morgan
SDL Releases the SDL Digital Experience Accelerator 2.0 - Bart Koopman
Switching to the DXA 2 Model Service In your DD4T Application - Quirijn Slings
SDL Tridion Sites DXA features Data sheet
What’s new in this DXA 2.0 release
SDL Digital Experience Accelerator (DXA) version 2.0 introduces a new architecture and additional features read more
I hope it helps.