On 10 February 2010 23:46, Will Robertson <[log in to unmask]> wrote:
>
> 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.

I think that's the wrong way to look at it. The right question to ask
is how many people willing to switch to LaTeX3 will be at the same
time unwilling to use LuaTeX. Depending on the answer, sticking with
eTeX as a base is either a wise decision or useless restriction.

> 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.

This is irrelevant, IMO. We are not talking LaTeX2e, where it matters,
but LaTeX3, which is yet to accumulate any significant amounts of
content. The backwards compatibility problem does not exist yet for
LaTeX3, why create one? In fact, sticking with pdfTeX might prolong
its life beyond what's necessary.

In practical terms there will be some sort of latex3[.exe] program
provided by TeX distributions to compile documents in LaTeX3 format.
It might as well point to LuaTeX engine and no one will know any
better.

Cheers,

Tomek