I'm at least 85-90% sure that Indy 2008 will be titled Indiana Jones and the Staff of Kings, which you can read about on IndyJones.net (
http://www.indyjones.net/). LucasArts told us at the beginning that the Ancient MacGuffin would be another biblical artifact that Indy seems to chase every other adventure (Ark - yes, Sankara Stones - no, Holy Grail - yes, Atlantis - no, Tower of Babel - yes, Heart of the Dragon - no, now Staff of Moses - yes!), and there have been whispers around various forums for a while now.
The trademark seems to confirm all that, and it's fairly recent - August 2007. Which, if the rumours of the game starting production again were true, then that would fit in right at the start of the new team taking over.
What do you think? I was personally betting on the Spear of Destiny, as a big wooden stick seems a bit dull. I think they'll jazz up its power a bit, much like the Tower of Babel housing the Infernal Machine.