Whoops. Following news earlier this week that Lego Indiana Jones was to include four-player co-op, MTV Multiplayer's Stephen Totilo - the original source of the news - has just posted this, saying that LucasArts got it wrong.
“LEGO Indiana Jones: The Original Adventures’ will feature the user friendly drop-in/drop-out two-player cooperative feature that players have come to know and love,” the game’s producer, Shawn Storc, said in an email. “However, we are not expanding this feature to a higher player count. I certainly do apologize for any confusion that has arisen; we must have been in a LEGO induced haze at the Collector’s Party.”
That's that cleared up, then.