The timing is clear. Applied expects to sample widely late this year and everybody (6+ companies) will have something shipping or sampling in 2014.
Impact is less clear. This is a relatively small volume market where Intel has had $100+ ASPs that will likely now be closer to $20. Can you hear the gears grinding?
ARM is not doing much by themselves, other than proving some "good enough" stock chips. It's all the other companies who are using ARM that you should be looking at, and some of them even have their own custom ARM cores. Also HP is already using ARM servers, and they will probably expand on it.
ARM would appear to have a limited appeal for servers in the data center but for the fact it is an energy-sipping technology. Once 64-bit ARM chips are available, we'll see. Charlie Babcock, editor at large, InformationWeek
I think many underestimate the impact that silicon photonics could have. Silicon photonics will eventually allow for optical chip-to-chip data transfers that will drastically reduce energy consumption.