I could see a blurring between platforms, where they kinda spec out something that uses the Threadripper socket, but is rated for less power, maybe uses a cheaper mechanism, and other things that would help push the costs down, but would enable features beyond AM4, but they could segment Threadripper systems from. And then have $500-800 chips. And then Threadripper becomes a bit more premium ($1000-3000 chips). Segment it so that the middle one gets 4 memory channels, but Threadripper gets 6-8, and fewer PCIe channels, and some other aspects (rated for lower TDP, maybe top it at 120-150W, while Threadripper is 150-250)
Or maybe they wait until a socket change (AM5). Keep it to 3-4 platforms (assuming mobile is kinda its own for the 4th one). AM5 grows, and covers consumer and HEDT (with 4 or maybe even up to 6 memory channels), partly so that it can also accommodate larger GPU (maybe they have it so some of the memory sockets take GDDR modules). They keep AM4 as a budget option. And then EPYC grows, with Threadripper basically being single socket version of that (with EPYC moving to support 4 or maybe even more sockets), and its got 8-12 channels of memory per socket.