This increase is sustainable.
To a certain extent that might be true, but we can't just assume that the market will continue to go up without experiencing some pull backs. If speculators get the impression that the momentum is slowly fading away, then they won't hesitate to cash out a large portion of their profits, resulting in a correction. Honestly, I don't think we are very far away from reaching that point. I say the top for now will be $1400 to MAX $1450, where after that a correction will happen. I use Bitstamp as reference exchange.