The reasoning by Linus for the change to end the Linux 2.6 series came down to "voices in [his] head" with the numbering now getting high with the next kernel, if released as is, being the Linux 2.6.40 kernel. This year also happens to be the 20th anniversary of the Linux kernel.
This morning, Alan Cox has proposed eliminating lots of the old cruft from the Linux kernel as part of this change.
Can we drop most of MCA, EISA and ISA bus if we are going to have a big version change? A driver spring clean is much overdue and it's all in git in case someone wishes to sneak out at midnight and bring some crawly horror back from the dead.
Linux users can already configure their own kernel to be compiled without most of this old code that's only used by ancient computer hardware, but many would like to see the Linux kernel trimmed down and become more lean. We'll see if it happens...