Here's what I suspect their strategic angle on this is:
I think when MSFT talks about HTML5, what they tend to mean by it is web applications with desktop-like rich UIs, fancy graphics (that, in particular, require hardware acceleration on powerful PCs to run smoothly), etc. They have decided it's in their interest to encourage the proliferation of such applications (expect to see a lot of tools to help this along - Microsoft have already released an Adobe Illustrator plug in to export to HTML <canvas> (http://visitmix.com/labs/ai2canvas/) and Blend 5 is strongly rumored to support SVG/<canvas> as a target platform) for two reasons:
1. They think it's a chance to differentiate their web properties, especially by moving them toward a rich-client model in which they already have experience. They tried to do that with Silverlight previously but didn't get enough acceptance from various quarters. They probably think it's an opportunity for their development tools business as well (in particular, <canvas> being a low level API leaves a lot of room for new frameworks on top of it).
2. If rich-UI, CPU/GPU-hungry HTML5 sites become common, people who haven't upgraded in a while will need newer browsers and PCs to view them correctly. Of course, Microsoft is hoping to encourage them to move to IE9 and therefore to Windows 7, but even if they go to another browser instead, if they're on older computers they'll still need to upgrade their PC for the sites to run well, regardless of what browser they're using, and by default that means moving to a W7/8/ ... machine. I think this is probably the most important consideration for them.
I think when MSFT talks about HTML5, what they tend to mean by it is web applications with desktop-like rich UIs, fancy graphics (that, in particular, require hardware acceleration on powerful PCs to run smoothly), etc. They have decided it's in their interest to encourage the proliferation of such applications (expect to see a lot of tools to help this along - Microsoft have already released an Adobe Illustrator plug in to export to HTML <canvas> (http://visitmix.com/labs/ai2canvas/) and Blend 5 is strongly rumored to support SVG/<canvas> as a target platform) for two reasons:
1. They think it's a chance to differentiate their web properties, especially by moving them toward a rich-client model in which they already have experience. They tried to do that with Silverlight previously but didn't get enough acceptance from various quarters. They probably think it's an opportunity for their development tools business as well (in particular, <canvas> being a low level API leaves a lot of room for new frameworks on top of it).
2. If rich-UI, CPU/GPU-hungry HTML5 sites become common, people who haven't upgraded in a while will need newer browsers and PCs to view them correctly. Of course, Microsoft is hoping to encourage them to move to IE9 and therefore to Windows 7, but even if they go to another browser instead, if they're on older computers they'll still need to upgrade their PC for the sites to run well, regardless of what browser they're using, and by default that means moving to a W7/8/ ... machine. I think this is probably the most important consideration for them.