fg,
I think you are right in terms of growth- access to markets will almost certainly be the limiter top future expansion.
That's not the same thing as a bubble. We make real and enviable profits on the business we do now. If EK just stopped at it's present size it would be a major airline with a long-term profitable business model.
The trick will be to stop when it is as big as it CAN be, not when it as big as the owners would LIKE it to be....