Linux will work just fine on new stuff as well
...just that, IF YOU BUY A COMPUTER WITH WIN8 ON IT, you'll have to turn off the signed bootloader thingy.
Talking about messing with the keys is a red herring; if you want to do signed linux, you were always going to have to install your own keys, and even if the UEFI spec doesn't specify how this is to be done, it ain't Microsoft's job.
They key points is that MS have said that to get their shiny sticker on OEM PCs, they not only have to ship with a way to turn off these security features, but they have to be customisable. This will, in fact, make key-signed linux MORE likely than it would have been last week.
As to the ARM stuff, in the abstract this is annoying. But in reality, I can't see the presence or absence of the ability to load linux onto win8 phones and tablets affecting me one way or the other.