Well, it would seem that they've just announced the concept for the XO-3, which will be tablet-based.
Now, it's said that they're going to try and bring this in at under $100, and I've even seen the figure of $75 mentioned. If they decide to launch the Give One Get One scheme for this one - where I buy two laptops, I get one and a child in the developing world gets one - then I'm definitely on that bandwagon! :o)