ordinary users may have to change to a system Since you ask for comments ... My expectation (as I've expressed more than once to Frank, Will, and others, by email and in person) is that any such latex3 format will be invoked as "latex3", and "latex" and "pdflatex" will remain entirely unchanged, invoking latex2e. Thus no users would be affected unless they choose to be. Otherwise, as far as I can see, essentially the entire LaTeX-using world will be broken, and that will harm everyone. Best, karl