You can't coordenate such big group. Otherwise there would not be any bubble in any market.
And even if you could, then outside people would see it as big market manipulation, since if you can agree to stay at the 1500's, then you can agree to put it back to the 500's and then rise to the 1500's, making a huge profit in the meanwhile.
Exactly. It's not as easy as what you are suggesting, plus this kind of artificial price hike wouldnt be good for bitcoin. We need natural growth which will hopefully come along gradually with adoption.