Being that C++0x was expected to come out between 2000 and 2009, they abbreviated 200x to 0x. Nothing hexadecimal related.
C++0x is considered to be the first major revision to the C++ standard, which, as said above, has been around for just about a decade. The following features are some of the things we should be expecting from C++ next year (with comments!):
- multithreading support (this will ease development for many C++ frameworks)
- lambda functions (inherited from C#... sorry for the pun)
- automatic types and type determinations (did anyone say auto from C#?)
- improvements in templates
- generalized constant expressions (I've been waiting for something like this for a while now)
- initialization problems fixed
- range-based for loop (seems like the for..each loop in Java and foreach in Python)
- better ways to create objects
- fixes to enums (strongly-typed now)
- user-defined literals
- upgrades to the Standard Library
- tuples (the good old days of Haskell...)
- regular expressions (now Qt doesn't have to have a QRegExp class anymore)
- a better way to generate random numbers (finally!)
Even with all these new features, C++0x is still going to try to be backwards-compatible with C++98 and C99. More detailed information can be found here and on this blog.
Others, however, argue that existing C++ frameworks and APIs won't benefit much from the upgrade.