Unicode 5.0 will be released in CY06Q3. Refer to the following URL:

http://www.unicode.org/versions/Unicode5.0.0/

Major changes from 4.0.0 to 4.1.0:

    * Addition of 1273 new characters to the standard, including those to complete roundtrip mapping of the HKSCS and GB 18030 standards, five new currency signs, some characters for Indic and Korean, and eight new scripts. (The exact list of additions can be seen in DerivedAge.txt, in the age=4.1 section.)
    * Change in the end of the CJK Unified Ideographs range from U+9FA5 to U+9FBB, with the addition of some Han characters. The boundaries of such ranges are sometimes hardcoded in software, in which case the hardcoded value needs to be changed.
    * New Unicode Standard Annexes: UAX #31, Identifier and Pattern Syntax and UAX #34, Unicode Named Character Sequences, and significant changes to other Unicode Standard Annexes.

Unicode 5.0 (beta) includes (diffs from 4.1.0):

    * addition of more than 1300 new characters (5 new scripts)
    * full interoperability with the most recent versions of GB 18030, JIS X 0213, and HKSCS
    * case mappings update
    * improvements on text segmation
    * tightens conformance requirements on Bidi implementations
Unicode 5.1 was released on April 4, 2008. We should support it.
For details, see http://www.unicode.org/press/pr-5.1.html