what will it be in the future?
It'll still be very fast?
Time isn't going to make it any worse. Games will still love X3D cache. Games won't be hamstrung by DDR4, just like they aren't now. But I think I understand you better: you don't want to buy anything, and hold out for AM6.
...But that's a loong wait.
If it's in the budget, you shouldn't skip out on an AM4 refresh you can enjoy in the intervening years. It's not going to be obsolete 3-4 years from now, but its affordable enough that upgrading to AM6 from it would still make sense.