Similarly, the Buffy and Angel comics done during the series were non-canonical and only those done after, with Whedon directly supervising, were canonical.
Although if and when a new Buffy or Angel TV show or movie came to pass, those comics would be "de-canonized" so fast your head would spin--because nobody in their right mind would expect the TV audience to have kept up to speed with the comics.
Of course, I don't think we have to worry about any new on-screen adventures for these franchises. I'd say if Whedon had any intention of doing so he wouldn't be supervising comics to continue the storylines of the shows.
Hell, some would argue it was a foregone conclusion since its opening weekend in theatres that Serenity would be the last on screen adventure for the Firefly verse, yet we didn't see comics set after the movie until this year.