Never did hear anything regarding low stock warnings on LE items. I may PM Tim at Weta about that one, but I hate to bother him. They're quite busy these days.
Weta hasn't said anything about the next environment. They seem to have had one ready to launch for The Hobbit last fall, but pulled it back when PJ announced he was switching to trilogy format. I'm guessing this means it's something we'll see in the next film; I'd bet it's Beorn's Hall or some part of Erebor, although I have no idea if we'll see that far into Wilderland by the end of Desolation of Smaug. Judging by the movie's title, it's likely. There's a crap ton of polls going on over on SF, people (new members especially) are absolutely pining for more LotR environments but I don't think we'll get any. The polls from the last two years indicate we'd see Grond, Minas Tirith, or Minas Morgul next, but I don't think Weta has anyone seriously working on those, not with The Hobbit in the works.
I do know that Richard Taylor offically "Greenlighted" The Green Dragon and Bywater Bridge environment, but production design has stalled. It's slow work as is with the team working on pieces from the new movies, and Daniel Falconer and Dave Tremont are still trying to figure out the best way to get both of the parts-the Bridge and the Inn-on one base without making the footprint too large or losing detail in the process. It should be something we'll see in the future, but it might be awhile.
Come to think of it, Weta has been very quiet lately. I'm assuming they're pretty heavily hit with workload right now, and I think they're just watching public opinion; the Weta forum is "What would you like to see" poll Hell right now. No doubt they're working up a lot of goodies for SDCC 13. I wouldn't e xp ect a shortage of polystone statues and prop replicas in the future; that seems to be the direction they're heading lately.