All specs aside, I really think that this is a knee-jerk reaction to the market / sales.
With the Tamron getting to market first, many fans held out. But as delays came on folk began to jump ship - especially when the price was verified by the vendors.
With the v1 24-70 gone, all of the sudden sales are down, even with a proported fatter margin on the v2.
We've all read the rumors that there was an IS version being tested - but this all went out the window once the v2 was Announced.
I disagree. It's not like they could design/test/set-up for manufacturing all since the 24-70 MkII came out. That's too little time for such a reaction. I'd be very surprised if they ever update the 24-105L after this new lens is on the market. With rationalisation of their zoom range, Canon's new blurb after December:
"Complementing the EF 17-40mm f4L USM and EF 70-200mm f4L USM, the 24-70 f4L IS STM lens completes Canon's f4L-series zoom lens range."