First big crash will come when the supply of newbies dries up.
There are still thousands a day signing up and pumping money in right now with all the hype.

But first big crash could see the casual investors trying to withdraw in a panic, and failing.. if there is a run on the exchanges.

Ether could hold its value better when bitcoin falls.
There are hundreds of programs getting built on it for the contract ability, so maybe not quite so purely speculative.