What do we know about this new series of adventures? Its labled HS1 and is a heroic tier adventure, but what does the "S" stand for? Why are there metallic dogs on the front cover? It looks like it would be the cover for an Ebberon adventure, but I don't see that on there anywhere..
Don't know much about it, but the monsters on the cover are most likely iron defenders which are from the first MM.
I think HS1 is to set it apart from the H1 series.
It can't be H4 because that would imply a Heroic adventure that takes place after H3 Pyramid of Shadows (after H3 you should progress into Paragon tier, with something like P1).
I'm not sure why they chose an S, but I think it's to differentiate the series. Next would be HS2, and HS3, and then PS1, and so on up to ES3. That is, if my line of thinking is correct. Could be wrong, just "thinking aloud", you know.
Hmm... maybe it will be a heroic tier only series. They may get sued by Sony if the Paragon tier is labelled PS1, PS2 and PS3. 
The S stands for the campaign arc the adventure is placed in, titled "Shadows over the Nentir Vale." I actually came up with that for a campaign title back when Thunderspire came out, but never used it. I was quite suprised to see that Wizards had the same idea. The second adventure is HS2: Raiders of the Stonemarch. No real info on that one yet.
Good info, folks. Thanks. That's right about the iron defenders in the monster manual.. I don't have a problem with the idea of a construct like a suit of armor or something, but I guess I just don't like "flavor" of an iron dog in my fantasy world.. Certainly not on the front cover - ugh..
My hope is Wizard's is really going to step it up with this new series. Their adventures have been... lacking for the most part. My biggest (and nearly only) disappointment with 4th Edition.