Rocket Lake might be 8 cores max on desktop.
Rocket Lake on mobile looks to be a fail. Tiger Lake is going to be a far superior mobile platform, and RKL is only there to fulfill volume.
Right now Comet Lake provides better CPU performance, and in some cases the battery life is better. Icelake has a superior GPU and media, and it has better integration. So both have niches, and due to the 14nm supply issue, it seems number of laptops using them are quite balanced between the two.
Icelake-->Tigerlake: Upgrade in all fronts
Cometlake-->Rocketlake: Downgrade except for the GPU
If they go the MCM route, it'll result in more power consumption and reduce CPU performance as it doesn't really have clock headroom and the IMC is likely going to move to the GPU portion of the die. EMIB will improve things a bit, but that's all.
OEMs are probably going to ignore Rocket Lake mobile for the most part(as I expect the same will happen with 28W Tigerlake - 25W cTDPup does everything).
The possibility of using Skylake cores again recalls my back-of-mind belief that whatever they say they'll do is always true for the far future than anything coming soon. What I mean is their claim that cores are backported may only happen with some post Sunny Cove based variants, or may not happen at all.
Rocket Lake is better for desktops, and the much improved GPU will make it useful for vast majority of the market. You can use pricing and move the lineup around to compete. The problem is on the high-end, because the top core count is limited to 8.
@jpiniero If they are moving 8+ cores to HEDT it won't help them. 10 cores on HEDT will end up larger than on client because its based on their server die with extra I/O.