According to a message sent out to Xbox live subscribers, Microsoft is planning to unveil something even bigger than the pre-launch Project Natal during their press conference tomorrow at this year's E3 expo.

"E3 is the world's largest gaming show and the place where we make the BIG announcements about what's coming up on Xbox." read the message. "With the massive Project Natal announcement at last year's event, you'd think we'd find it hard to top that. Well, think again. This year at E3 we've got even BIGGER announcements to share with you."

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More on Project Natal:

Microsoft Xbox 360 Natal first play at E3

Project Natal to hit Xbox by Christmas

20 Project Natal games we really want to see

Project Natal launch expected in October

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So, further developments on the Natal front? Or the arrival of the Xbox 360 Slim? Something completely new altogether? Shameless PR posturing? We'll keep you posted after Microsoft's Natal conference, which starts Sunday at 7pm PST (or 3am for UK-based Microsoft early birds).

Meanwhile, let us know what you reckon in the comments.