Don't know if this gives anything away or not (I haven't kept up on the "spoilers" page), but I do watch Amazon closely for news about new books related to Indy 4. Typically the descriptions are not included this far in advance (and to keep plot points under wraps).

However, while on Amazon's UK site this evening, I noticed that two new books were listed. Both are meant for very young readers and detail parts of the Kingdom of the Crystal Skull story that I don't think have been revealed yet. I've copied the description below. I wonder if "Ox" is Ray Winstone's character and "Mutt" is Shia's. It all makes sense given the descriptions and what we know of Shia's presumed relationship to Indy and Marion (his kidnapped mother?).

Check it out:

Title: Meet Indy: I Can Read (Indiana Jones and the Kingdom of the Crystal Skull)
Publisher: Harper Collins Children's Books; Film tie-in edition (May 5 2008)
Page Count: 24 pages
Description: Meet Indiana Jones. Archeology professor at the prestigious Marshall College, adventurer and hero. This easy to follow book is perfect for young readers, just starting to read alone and packed full of photos from the new Indiana Jones movie, Indiana Jones and the Kingdom of the Crystal Skull. Indiana Jones has been all over the world, on exciting quests for missing artefacts but now he has settled down, as a college professor. But when a young man called Mutt thunders into his life with a cryptic letter from his old pal Ox, Indy is drawn out into the adventure of his life. Follow Indy and Mutt on their fun adventure in this easy to read story, full of cool new photos from Indiana Jones and The Kingdom of the Crystal Skull.

Title: Meet Mutt: I Can Read (Indiana Jones and the Kingdom of the Crystal Skull)
Publisher: Harper Collins Children's Books; Film tie-in edition (May 5 2008)
Page Count: 24 pages
Description: Meet Mutt Williams. Wily rebel about town and new sidekick to none other than Indiana Jones. This easy to follow book is perfect for young readers, just starting to read alone and packed full of photos from the new Indiana Jones movie, Indiana Jones and the Kingdom of the Crystal Skull. Mutt Williams is a real rebel, dropping out of prep school after prep school and spending more time working on his motorbike than his school books. But when his mother and their old friend Ox go missing, Mutt turns to the one person who can help him, Indiana Jones. Follow Indy and Mutt on their fun adventure in this easy to read story, full of cool new photos from Indiana Jones and The Kingdom of the Crystal Skull.

Meet Mutt
Meet Indy