It's pretty interesting to see Microsoft edging out onto this limb of abandoning their long held policy of supporting their software for long periods of time. There is pretty much no alternative, so on the one hand it is not like their enterprise customers have anywhere else to go. On the other hand, it's one less argument for companies to stick with Microsoft if they are already on the edge. I'll be interested to see how it turns out if they keep pushing in this direction.
This IE "change" isn't so much an abandoning of their long held policies as clarifying them and fixing some wrong assumptions companies had made in the past. Microsoft's support policies for the OS components has long held that what they will provide (extended) support for is the most recent Service Pack version that has kept up with Windows Updates. For various reasons, companies have tried to take advantage of the fact that IE is an OS component to qualify it for extended support and also taking advantage of the concept that IE updated/versioned at a slightly different pace from Windows Service Packs to assume that they could claim the extended support timeframe for an individual IE release as if it were entire OS versions.
The amazing thing is that Microsoft took this long to correct what should have been an obvious mistake: that IE versions apply like other Windows components and they should only need to support the most up to date one for that OS version.
The kind thing here is that Microsoft has taken ownership of that mistake, publicly admitted that they made it and that the fix was coming, and given companies more than a year and a half (and advertising to that effect, such as the site linked here) to adjust to the fix.
