Do you have a source confirming that you won't be able to upgrade?If you choose ddr4 option you won't be able to upgrade, Raptor Lake will be full ddr5 which is fine because by that time ddr5 will be cheaper and faster, and ddr5 only controller wont have compromises as hybrid solution, but if you choose now ddr5 you will overpay it by massive amount, and also no performance benefits because early ddr5 versions are slow.