They could, but that's more than just an easy money grab. Something Nvidia would already be familiar with from Tegra.
What seems more likely/risky would be nvidia starts charging a premium for a Mali replacement, or begins sandbagging Mali on the lower end of things. But Qualcomm already has Adreno to defend against that.
The latest Tegra SoC launched March of 2020.
On mobile SoC margins I guess that margins are low because there is a lot of competition - start cutting off IP to the competition and margins will rise.
I suspect that their focus will be on the server / automotive to start off with but the very fact that they can to any of this is troubling for me.
EDIT: correction, make that the last generation or four (oops, time flies)
It all happened because Apple came out with the first 64-bit design, and QCOMM wasn't ready. Rather than deliver 32-bit for 1 more year, they used an off the shelf ARM 64-bit design (A57) in their SoC called the Snapdragon 810, and boy was it terrible.