I think Pentium will still be supported. i486 refers to very old 32 bits CPU (80486). The article is not clear but by default I tend to think that i586 and i686 will still be supported.

"Pentium" also refers to a 30-year range of CPUs with very different capabilities. I suspect that removing (say) P5-specific kludges would also not cause too much grief given it's over thirty years old and dates from about the same time as the newer 486s. At some point you need to clean out the cruft a bit.

Support for the Pentium isn't going away now, certainly, and nobody's announced plans to drop it from the Linux kernel, but every architecture has a time horizon.