Ryan over at Hawiiweblog has revealed that the Lost crew is filming over at Honolulu Airport, which is meant to double for LAX.  The season 6 premiere episode is entitled "LA X" (space is deliberate), so it looks like some of the crew WILL be landing at the Los Angeles airport.  Specifically, Ryan reveals that:

Indeed, expected on the set were Matthew Fox (Jack), Evangeline Lilly (Kate), Josh Holloway (Sawyer) and Naveen Andrews (Sayid). But the first hardworking actor sighted was none other than Daniel Roebuck, who played the hapless (and previously detonated) Dr. Leslie Arzt.  [Ryan has provided a photo of directors' chairs for some of the cast members - although Matthew Fox's chair isn't there].

Your guess is as good as mine about what this means.  Will everyone simply step off the plane at LAX and not remember the island?  What's interesting, is taking this in conjunction with the next report.

Over the EJ reveals that he saw filming take place in the jungle over at the Swan dig site:

Looks like things pick up immediately after Juliet hits the bomb because the construction site looks like the Swan after it got sucked in. Jack, Kate, Sawyer, Miles, Jin were there. Saw Sawyer upset over Juliet's actions and runs toward the hole which is now stuffed with all the metal from the site. Also saw them and some stunt doubles clumb out of the hole using vines/rope.  Didn't see them filming, but saw Hurley and Sayid around set. Sayid's Dharma uniform was covered in a lot of blood so it looks like he's still hurt from last season.

I also read (though I can't remember where) that filming also took place over at the four-toed statute and appeared to pick up where we left off (presumable with FakeLocke, Ben, Richard, Sun, etc).

So, if we put this all together what do we get?  Well, it's all conflicting right.  It seems that Kate is at LAX and still at the Swan site.  If those scenes presumably take place after the explosion, then it's possible that the two Kates exist in separate realities.  Could one version of our survivors have stepped off the plane in LA while another version is still in the 1970s on the island?  ARGH!  Brain hurts....