I agree with you. Their cloud is really the danger in this relationship. Educators should use products and services whose business model doesn't hamper their ability to remain in control of their students' education. I didn't mean to come off as saying Google isn't sincere and another company with similar offerings would be. It's business.

I think it will get beyond individual school/department lock-in though. Steam, for example, hasn't simply locked-in consumers to their purchases and made it difficult to transition away. Developers are often locked in because they rely on Steam for match-making, piracy-busting, cloud saving, achievements apis, server-hosting, modding support, etc. etc. All of this offloaded centralization is easier than doing it yourself and more like the console's devs are used to. If you want a AAA PC game, you're more than likely going to get it exclusively on Steam.

Android is already there, many/most of the apps require Google's services for even mainline functionality and definitely for consumer discovery. Google education could be next if it gets adopted like Google Analytics as the de-facto api, educators would have no choice in the matter. All good products use Google's apis for everything.