He's extremely reliable. It depends on how solid his source is for that particular piece of info and how confident he is in it, though.
Insomniac being Nextbox exclusive for a title wouldn't be surprising. I doubt EA wants to publish another one of their games with Fuse being a massive bomb, so they're going to need another publisher. Microsoft may want them on stage just like Sony trotted Bungie out on stage, but I don't see it having the same impact.
Sadly, Insomniac's output has been mostly garbage the past gen, but I still enjoy me a Ratchet game every now and then (Crack in Time was great).
I wish they'd stop trying to follow everyone else, their games just look generic and have a sterile feel to them.