And old-world flying is cata only if I remember correctly.

huh in that case it doesn't really seem worth my $68 bucks to upgrade. I wonder if old world flying is cata only, that doesn't really makes sense to me.

You can't fly till lvl 60 anyways, so you won't really miss out on the old world flying if you only play till the 20s ;)

Old World flying is definitely expansion-only. Partly, it's just a perk of buying the expansion, but there is also a more practical reason. They need to keep people out of the new zones like Hyjal and Twilight Highlands until they buy the expansion. If they allowed Old World flying to anyone, it would be a large pain to keep people from just flying into places they aren't supposed to be. Blizzard could throw up a bunch of invisible walls, but that's really annoying and a lot of unnecessary work. A much simpler and more elegant solution was simply to restrict flying to Cataclysm-only. Problem solved!

Much of the zone redesign and work that went into the expansion was done to enable old world flying. It makes a lot of sense that they wouldn't let you have that if you don't pay for the expansion they spent a lot of time and money to develop to make it possible. It makes as much sense as not giving you goblins or worgen, either, unless you buy the expansion.

hmm, does that mean Warlock summons won't work in the new zones? Or maybe some level restriction eg

You can't summon a < lvl 80 into a new zone