Totally -- but it takes balls to acknowledge that. I'd certainly feel betrayed if I had been a loyal SproutCore user: templates for the user interface is almost a complete 180° from the prior gospel.
But from an outside perspective, I think this could make SC truly competitive, and that's going to be a good thing for JavaScript-heavy web apps in general.
I'm not actually sure if the idea of templates alone is that much of a departure, I could see something template like working in Cappuccino (a more human readable version of a XIB perhaps), but relying on HTML and CSS is something I'm obviously not crazy about.
But from an outside perspective, I think this could make SC truly competitive, and that's going to be a good thing for JavaScript-heavy web apps in general.