The competition doesn’t need to be open, they just need to motivate Google to be open.

...but could that actually happen? I'm not sure what WOULD motivate Google to be open. Even if there were three or four more major mobile players (all with equal market share), and Google had the only platform that allowed unblessed software to be installed, I'm not sure that would pressure Google to continue to be "the open choice", but more likely to take this same action as "the odd man out".

At a fundamental level, there is an illusion/concept planted in the human mind that "force answers everything", and when they run out of ideas (or all the ideas that they have would require too much [re]work to their liking) the tendency is to fall back onto "just use force" as an easy "solution".