I wrote:
The performance of #invoke should be OK for modules up to $wgMaxArticleSize (2MB). Whether the edit interface is usable at such a size is another question.
The Wiktionary folk are gnashing their teeth today when they discovered that in fact, loading a 742KB module 1200 times in a single page does in fact take a long time, and it trips the CPU limit after about 450 invocations . So, sorry for raising expectations about that.
-- Tim Starling