The LAS 1.4 Specification was approved by the ASPRS Board on November 14, 2011. You can download a copy of it here:
See this ASPRS press release.
After a long summer of often contentious debate the ASPRS LAS committee has decided to maintain full backward and forward compatibility according to Martin Isenburg. He also noted that it includes new Extended Variable Length Records (EVLRs) that allow appending information such as geo-referencing or spatial indexing to the end of the file without having to rewrite the entire file. And it defines a new Extra Bytes VLR that allows to add and self-describe additional attributes for each point such as echo width, normalized reflectivity, or shading normals.
Kudos to all involved for all of the hard work.