what would it upgrade?
ddr4, no
quad channel ram, no
pcie3, why?
more power deliver specs, not needed
sata? thats the southbridge anyway and works quite well across all boards, even cheap ones.

if they are going to change things, it hurts compatibility going forward or backwards. if steamroller is only a modification to the prior chip, then theres no point changing the chipset just a little. they should be planning on how the next chipset will accomplish all their needs in a better package than the current one.

am2 to am3 was a very nice smooth transition, but limited the changes. if they start over knowing that all cpus will have a gpu built in (even a tiny one) they can get a single platform to cover the fusion chips and the beastly cpus chips. and if they only had to design one chipset to rule them all, it could be a really nice one with all the bells and whistles.