Valve have put up an official explainer on why we haven't gotten released dates or pricing for the new Steam Hardware like the Steam Machine and Steam Frame.
You don’t have to update all the parts at the same time. Sure, if your motherboard/cpu/ram fails you’ll likely need to replace all 3, but your current graphics card, PSU, case, etc should still be fine.
Plus, if you’re going from a 10 year old rig you could buy used DDR4 era parts on EBay or Facebook to save money and it’d still be an upgrade
You don’t have to update all the parts at the same time. Sure, if your motherboard/cpu/ram fails you’ll likely need to replace all 3, but your current graphics card, PSU, case, etc should still be fine.
Plus, if you’re going from a 10 year old rig you could buy used DDR4 era parts on EBay or Facebook to save money and it’d still be an upgrade