Found this at DarkUFO
The LOST crew and filming have returned to Windward Community College, which is the Santa Rosa Mental Hospital set where we last saw Hurley (Jorge Garcia) in a flash forward during the Season 4 premiere. Not only is the crew back on the set of Santa Rosa, but both Garcia and Matthew Fox were spotted on set with some doctors and orderlies. Also pictured was Jack's truck!!
Now, what episode is being filming is a whole different question. We have seen set pictures for the potential Sayid or Ben FF in Episode 4x09 and Kate is rumored to have episode 4x10.
However, today's filming suggests a potential Hurley or Jack Flashforward once again. Well as Ryan mentioned, the only real clue we got was the appearance of a doctor who could fit the casting call for Dr. Stillman for episode 4x10.
Is it possible that the crew is working on a Oceanic 6 Multi-Centric episode?? Is this the filming of the rumored Jack Centric finales!? Perhaps it is just another Hurley FF!?
”LOST” returned to the Windward Community College campus in Kaneohe today to film another scene at the “Santa Rosa Mental Institute.” A sign was set up in back, fronting a sometimes soccer field, and Jack’s old pickup truck was parked nearby. Filming took place inside Hale Kuhina, the continuing education/employment training building, with Jorge Garcia and Matthew Fox. A man dressed as a doctor (Dr. Stillman, perhaps, given recent casting calls) and a couple of burly orderlies were also sighted milling about.
Hale Kuhina is within a stone’s throw of the Hawaii State Hospital building and shady tree that served as the Santa Rosa lawn where Hurley received a mysterious visit from Charlie.