There's a
sneak peak at an Order of the Phoenix Lego set floating around the internet today. It's another castle. This is fairly consistent with prior patterns in that Movies 1 and 3 had castle sets associated with them and 2 and 4 did not.
This castle is a bit smaller than the other two castle sets, but the current MSRP is also a bit less (IIRC). In terms of physical size, it is probably closer to the Dumbledore's office set from CoS than either full castle but its brick count might be higher than previous castles owing to the blockier, and probably sturdier, build of this one. The Gryffindor tower bedroom segment of the PoA castle set was similar to some of what is going on here so I guess that was a transition stage in the design. In terms of colors and the like, it should blend in with previous castles fairly well, and perhaps link the large castle sets with the smaller classroom sets since the previous castles were more rounded and the classrooms tended to be more square and blocky.
I'm trying to decide who all the minifigs are. It looks like Harry (in robes), Ron (in Muggle clothing?), Hermione (in robes), Dumbledore (he's always looked the same), and Hagrid (he's always looked the same) as certain retuning minifigs. There is also a blond one that could be a Draco returning figure, but if it is Draco, it looks like a new clothing paint job for him (Muggle clothing?). The definite new figures are somebody in a black hood (looks like the executioner from PoA more than anything coming to my mind for OotP) and UMBRIDGE! Hooray for an Umbridge minifig! There is also a thestral. I can't wait for better images of that so I can see if they gave it a regular horse head and body or sculpted something new and skeletal. The legs in this pic look very different from typical lego horse legs, so there is hope!
If previous lego trends are anything to go by, I'd expect some, but not all, of the following sets for OotP:
Umbridge's classroom/office
DA meeting in the Room of Requirements
number 12 Grimmauld Place
A Ministry of Magic set for the final battle
Something from Hogsmeade
I'm not expecting a train set. 1 and 3 had trains while 2 and 4 did not but I think they'll save it for 6. The only reason to include a train this time would be for Neville and Luna minifigs and those can be included in the assumed DA and MoM sets. A train for 6 has so much more potential between the Slug Club meeting, spying on Draco, and the Tonks rescue (assuming all that makes it into the movie). Plus, they only did four sets for GoF (one for each task and the Durmstrang ship) so I'm not expecting a large quantity of sets this go round and I'd certainly prefer they do something new than make yet another train.