Greg Street, the mild mannered developer who has a secret identity as The GhostCralwer, recently did an interview with MMOZine. It's a pretty good read but there was a major clue as to the timing of IceCrown release and bosses.
MMOZine: Will all the bosses in Icecrown Citadel be made available immediately or are you going to stagger them, as you did in Sunwell Plateau?
GS:Well we've not announced when it's coming out yet but we don't want to throw players against challenging raid content right over the holidays, so we're trying to avoid that a little bit.
That would seem to indicate that we won't see 'challenging raid content' until after the Holidays. I would interpret after the Holidays to mean after Christmas and New Years. We may see the Lower Spire (the first part of Ice Crown) before December, but I wouldn't expect to see Arthas himself until January based on Ghostcrawler's response.
And just to underscore the point, Datth on the tech support forums just posted:
We only provide mirror links for full client patches. Background downloads do not count. You have around 1+ month to download this file so we're not really worried about your speed. :)
That puts 3.3 at December 20th at the earliest, probably more like after New Years before we even set foot in Ice Crown Citadel.