I think the only way for non-developers to ensure their site keeps step with feature enhancements is to invest in a premium theme that has frequent updates.
The theme I use—Dashi—was available for V5 within 24 hours, and has had a number of updates since I started a year ago. On another site, I have a customised version of Massively, but this hasn’t received any updates for some time. Fortunately, I don’t use Memberships, so the theme still continues to work for me.
Edit : I note that Newsportal is compatible with Ghost V5. So are you looking to carry over changes you’ve made to the .hbs files? I use an app called Meld to update the current theme with my changes. With V5 changes, some of my edits were redundant since the changes could be made directly in Ghost.