In my opinion, future proof means suitably powerful to fulfill your needs for the timescale you want. We have only recently hit the point where GFX is noticeably bottlenecked by my CPU, thus driving a platform upgrade... really, my main driver is scratching an itch and time for a second rig int he house... my Xeon x5650 and GTX1070 still runs everything pretty well (I'm playing catch up a huge games collection, so I don't have current AAA games).
AM4 maybe EOL, but it's wicked powerful and will be fit for purpose for a long time. A 5900x system will not suddenly become trash when AM5 launches. Lets be honest, games are the main cause for most people "requiring" an update, and that is best addressed with a new GFX card, not upgrading the CPU and mobo. AM4 is mature, and I think AM5 and DDR5 will come with a big price jump for the first year, and I am conscious of performance/£££ ratio.