This kinda of rumour I have heard since 2007, yeah, ten years ago! But it seems not that possible from the current view of AMD Ryzen processors! The following things could be counted as reasons,
1. Apple merged macOS development team to the iOS team, in other words, they put their focus on the ARM architecture rather than merely Intel architecture. Especially Apple acquired P.A. Semi more than ten years, which are the strong force to develop current Apple ARM processors.
2. From the current view of AMD Ryzen processor, it is another traditional processor, without supporting of hybrid architecture. In other words, even though using such processors, to make iOS apps run on macOS is almost impossible without emulation. And this is not what Apple expects, especially the focus switched onto iOS from macOS.
3. Intel is a strong player for x86 processors, the performance is not really a problem for Intel to catch up with AMD. In other words, Intel always expected AMD would give the world some a surprise, this surprise seems threatening Intel, but in fact this effort consolidates the important role of Intel architecture, when competing with other opponents, such as ARM, UltraSPARC, PowerPC and so forth.
4. In my own opinion, Apple does not need a second processor sourcing, they would still deploy Intel processors. If they find it tired, or tired of Intel, they would use their own ARM processors to take place of Intel ones, with some an emulation(s) like the days when Rosetta was provided to support old PowerPC applications.