In short, CTP Futures are things that may be added to the core release in the future, but today are just a preview.
But as you said that you found no info, In the main page (http://ajax.asp.net) , click on Feature matrix. There is a list of what is on CTP Futures and what is on the Core package. On the same page there are 3 links to the same document in diferent formats explaining the diferences.
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