I think they'll announce the SDK at MacWorld which is being held Jan 15th. Alongside the announcement of the 2nd Gen iPhone.
And in regards to the OP I'd have to say that I trust them as much as any other company, no more or less. I do appreciate their cohesiveness which makes things simpler, but after using my Eee for the past while the openness has been so cool. I'm just glad that both options exist :)
Let companies like Apple have their closed systems that are high on innovation and lead the way. Then let the Open Source community come along and do their copy-cat products that are a little rougher around the edges, but build upon the groundwork in a big way.