In the past, we've had some version changes like these in the past, at least once or twice.
It's a bit weird but not that confusing, and ultimately users don't care all that much, and usually even forget about it :-)
That said, I don't have a strong opinion.
To Russel's points, we might save us some time by just focusing on updates of 2.5 and 3.0, rather than the current 4 branches maintained.
Even if 2.6(9) and 3.0 are close, it's not critical if the numbers are close too.
So I'd tend to not even bother with renumbering at all.
But frankly, I don't mind :-)