4k transcoding

Looking to put this together with an internal Blu-ray writer, any advice would be appriciated...

So I've just started to look into building a home media server for Plex, and I'd like it to be relatively future-proof. Then "4k transcoding" comes in my mind, as I guess 4k may be the standard resolution for the years to come. I have little experience in this field (as to Plex, video format...