They said it was impossible... They said it made absolutely no sense... Dream on they said...
Last couple of times this was brought up here, most people said it made perfect sense, but is likely just about patent licensing.
There still is no proof of this being anything more than that. I still highly doubt that we'll be seeing AMD GPUs on Intel CPU dies, but I think we'll see some interesting things, namely from Apple, where we might see Intel CPU and AMD GPU on interposer or something.
I almost would say we might see Intel adopt Infinity Fabric links (maybe not on the CPU die itself though) to help their CPU and AMD GPUs communicate. But with AMD going full force into HPC with their CPU design, I'm not even sure of that since it seems like it'd be offering up a little too much since AMD has an opportunity to make inroads with their core and thread count advantage, so they'd want to leverage both their CPU and GPU. Perhaps not, or maybe even Intel and AMD will look at it more as a necessary thing to deal with Nvidia in that space. I think that is a key part of the deal is that it's more about both having to deal with Nvidia than competing directly right now.
Another thought that might make sense for Intel and AMD to buddy up on sharing interconnect like Infinity Fabric is that both are basically betting on it being an integral aspect of computing going forward, so getting it shared beyond their own stuff might be key. For AMD it's interchip communication (heterogeneous compute), for Intel it's Optane.
They could even collaborate on mobile. Take an ARM design (maybe tweak it a bit), pair it with a mobile focused GPU, put an Intel modem in it, and then produce it on Intel's fab. Heck maybe they could even make a super efficient ARM competitive x86 core. AMD could sell a cheaper variant that would take up wafers for their GF deal, and then Intel could offer a premium one that maybe has more cores and clocks higher, maybe it is the variant that gets the modem integrated.
That's wild speculation, most likely this is just practical licensing deal, with some potential for further benefit (i.e. Intel pushes for pairing with AMD GPUs, AMD sells more GPUs and gets some money in licensing patents with someone they already have cross licensing deals with).