The margins are likely extremely low and performance doesn't seem to be anything amazing, it's likely current or slightly last generation. Don't forget that consoles will still have to sell for <$500 and make some profit.
http://www.eurogamer.net/articles/digitalfoundry-future-proo...
For now. But sooner or later ARM will become powerful enough to run servers. The chips are cheaper. The operating costs will also be lower as ARM draws lower power. Before you know it data centers will switch over to ARM, first as a trickle, then as a deluge.
ARM will do to x86 what Intel did to SPARC & Alpha & PA-RISC & MIPS. Intel will have to keep retreating to higher and higher end niches.