Season 2 part 2 includes the New Aincrad, which was added into ALO. So, they could add more Aincrad stuff without the die-in-the-game-die-in-real-life element. It's also possible, though, for them to add content which fits into the timeline in the middle of season 1 part 1, although the problem with that is that Kirito and Asuna weren't on good terms until ~Floor 73, so there isn't too much room there to involve all the characters. EDIT: correction - floor ~57, so there is room. From floors 57-74 Asuna and Kirito's relationship is not greatly explored, although it's clear they never teamed up. Also, the anime's creators could release a season covering a different set of characters as the main characters, with Asuna and Kirito popping in.
I was also hoping that the Laughing Coffin guy would be someone from the first story arc, especially since they were flashing through all of the faces of people Kirito had met, which means they kind of implied it. I guess the third death gun was never arrested, although the characters probably know his SAO username from his real name, so no real room for surprises there.
I was glad to see more Asuna in Season 2 part 2. That was a very good story arc.
On the subject of a third season, they left a hanging plot thread at the end of the last episode of season 2. Kirito was just about to ask Asuna a favor when he was interrupted.
