My feeling is it will be net zero as far as ARM servers are concerned until the hardware is made and is viable. Perhaps Apple ARM laptops will help with marketing ARM as a viable option, but we already develop on OS X in order to deploy to Linux without any great calling for OS X servers.
Cloud server “hardware” has also drifted from what you see in real hardware. There are numerous times in my career I’ve had to explain to deveopers of all experience levels that their SSD is several orders of magnitude faster than the tiny EBS volume they’re reading from and writing to.
In short, I think architecture mismatch just isn’t that important to most Web App oriented companies. My girlfriend works at a travel industry giant and they’re at the opposite end, putting IBM mainframes to good use. They don’t have much use for Macs and most of their developers seem to be on Windows instead of anything resembling what they’re deploying on. For the segment of our industry that does care, they’ll have options and will choose them regardless of what Apple, Google, and Microsoft do with ARM, Intel, Power, MIPS and other architectures.