On 11/02/2010, at 8:42 AM, Philipp Stephani wrote:

> However, any of these has to be done quickly: If LaTeX 3 won't be finished before LuaTeX, it will be obsolete anyway.

LaTeX3 and LuaTeX are orthogonal; one does not deprecate the other. Certain aspects of the work the LaTeX3 project have done, such as the expl3 macro language, might become less useful when/if LuaTeX is the *only* widely used TeX engine. But until then LaTeX3 will not assume the presence of a Lua programming environment.

LuaTeX will not be backwards compatible with pdfTeX in the generated output (i.e., two identical documents may have slightly different hyphenation/justification choices and therefore different page breaks). While the changes will obviously be rather small, I don't think anyone can really predict when pdfTeX will stop being used.

-- Will