Here's the wall: could any competitor to Google itself ever be on AMP? (E.g., a competitor to search, Gmail, YouTube, or adsense/adwords.)
Or would it have to be something on the open web? And if only AMP pages get ranked well on Google in the future, how much harder would it be for such competitors to ever get noticed in the first place?
> And if only AMP pages get ranked well on Google in the future
Currently, the only thing on Google results explicitly limited to AMP is the mobile news carousel. Presumably AMP pages also do well on the "loads fast" evaluation that affects normal rankings, but in theory it should be possible to do equally well without AMP. If this is changed, or turns out to not hold up in practice, then there is cause for concern, but I have not seen evidence of either.
News sites, of course, don't generally compete with Google's core services - unless you count Blogger, but in that case all news sites do). The one thing I can think of is that they might embed videos hosted on competitors to YouTube. When it comes to that, AMP is a mixed bag. Unlike on the open web, video players that use custom controls/iframes (like YouTube) need to be explicitly approved, since there's not much alternative without granting a blanket license to put arbitrary sites in iframes, which would (mostly) defeat the purpose. So Google acts as a gatekeeper. On the other hand, the spec [1] already lists like a dozen random video hosts you've never heard of; that's not evidence that Google wouldn't try to block a more serious competitor to YouTube, should one ever spring up, but there's certainly no evidence that they would.
Unless I'm mistaken, they did experiment with various attempts to highlight their own video offerings beyond what popularity dictated before finally giving in and buying YouTube.
And we all remember the kinds of crap Google did to try to foist Plus on users who had no interest in it. At one point 1/4 of the annual bonus of everyone at the company was tied to it.
Or would it have to be something on the open web? And if only AMP pages get ranked well on Google in the future, how much harder would it be for such competitors to ever get noticed in the first place?