Yes. I can imagine it because they've already done so repeatedly. The first case I can think of was Apple working with IBM on the Taligent operating system (designed to compete with what became NT and NeXTStep) circa 1988. Then the PowerPC chip at the center of Macs for years was co-developed with Apple, IBM, and Motorola, and in later years IBM supplied the actual chips. Also, the Apple Network Server machines (circa 1996) ran AIX.