I don't think it's fair to say Microsoft never bought into jQuery. They've continued moving toward jQuery-centric approaches on both the MVC and WebForms front

I don't think it's fair to say Microsoft never bought into jQuery. They've continued moving toward jQuery-centric approaches on both the MVC and WebForms fronts, communicate to developers that it's the preferred approach for client-side development, devote development/testing resources to jQuery and jQuery UI, and threw out their MicrosoftAjax.js based validation for a new approach based entirely on jQuery and the jQuery Validation plugin (and I hear that's coming to WebForms as well). Even the WCF team has reworked their client-side examples and libraries stuff to be based on jQuery and less cumbersome. I believe what they're talking about regarding an "AJAX grid" is the idea of using an HTML helper to render a collection of data that matches up with what the upcoming jQuery UI Grid widget expects. You could still draw a parallel to server-controls there, but it seems harmless. Ultimately, it's the sort of thing we all end up writing ourselves anyway.