[acdha]

If Microsoft were serious about this they'd have released a ChromeFrame-style compatibility mode when IE8 came out which would allow admins to use group policy[1] to load the old rendering engine for poorly supported (i.e. all) enterprise webapps and use the modern engine everywhere else.

This is the same approach which will be necessary to address endemic security and reliability failures caused by bad architectural choices made for single-user desktops in the 90s. Since they finally shipped MED-V I suspect they'll probably use that approach and tell corporate customers that the only way to continue running IE6 is in an XP VM with some sort of on-demand launch scheme.

1. Setting an HTTP header would be easier but seems likely to allow phishers to opt-in to security holes and there's an argument that pushing the support cost off to app owners is better any way.