It will crash of course, the out of core tech is not yet developed AFAIK.
Arnold is slow in every aspect, it's a great production render, very solid, and it gives an astonishing quality, but it is in the Maxwell side of the fence, Quality at the expense of excessive amount of time.
Still as I've said GPU is not a good investment for me, at least yet, and I won't recommend to anyone for the ti,e being, I did in the past, and I was wrong I have to admit, maybe with the next gen (after the 980 family) it will be awesome, for the time being, with Corona in the game, I'll stay with CPU.
BTW I say all this because Corona exists, if there is no Corona I'll be back to GPU rendering, even with all it's flaws, but I prefer Octane, iRay or even RedShift if I need it to being back to mentalRay or having to acquire VRay.
Think also that having CPU nodes let me leverage those nodes for more tasks, like distributed simulations or giving a CPU farm personalized service to small artists and studios, the GPU market is not a good investment yet for me, and I have several GPU's distributed across my farm for GPU rendering.
But... for me... Corona wins! Hahaha
Cheers.