This represents the case of what seems to be happening with ASUS. In correspondence with ASUS support, a customer asked ASUS if they plan to update a Crosshair VII Hero X470 motherboard with support for AMD’s upcoming Ryzen 5000 series CPUs, the company gave a rather negative answer. Here is the quote below:
I am writing this email to provide you an update about your ongoing case. According to our engineers, We have no plans for the Crosshair VII Hero to support the Ryzen 5900X, please purchase Crosshair VIII Hero and any Ass (*ASUS) B550 motherboard that will support Ryzen 5900X and 5000 series processors.
You can check out the full Reddit thread here. It appears that ASUS recommends users that they upgrade to new motherboards and that there will be no support of AMD’s Ryzen 5000 CPU series on 400 series chipset on their motherboards.