Considering there hasn't been a V8 put in a Disco since 2012, I doubt a V8 will make it into the Defender. A six of any persuasion will be more than enough especially with electrical assistance.
As GB said, EV is the future, especially in Europe and the UK where ICE will be taxed to oblivion.
I think if LR could go full EV today, they would. MHEV and PHEV are all about bringing the people with you - much of the world is not ready for EV and these two options are about letting people dip their toe in the water (aside from getting more from less out of the ICE). It's a bridge to full EV.

