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.
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.
I wonder how far we are from the removal of all 32-bit x86 support from the mainline Linux kernel.
Maybe it's all ARM Cortex now? I thought the 386 was still in production.