Everything I've been reading over the past year has indicated that Superman Returns would be a continuation of the Donner movies
Thats from what YOU have been "reading" before this trailer/teaser arrived.

and that trailer certainly does not include anything that would indicate a complete reboot of the franchise (i.e. Batman Begins).
Really? Seeing glipmpses of him being sent to Earth, the Smallville backdrop, the voiceover regarding his trip and powers -- NONE of that smacks of a reboot? Of course, like G said, these could be flashback sequences to accompany a continuation-after-II story, but I doubt that.

You're telling us to watch the trailer carefully, but seems to me like you're reading a lot more into a teaser trailer than is actually there.
No I'm not; I'm saying watch the trailer carefully......and you'll see more than a hint of reboot flavor to it.