So what has Disney done this year to contort our public domain laws?
Let's also keep in mind the difference between copyright and trademark; even if art containing Mickey Mouse enters the public domain, that doesn't mean that Disney loses the trademark to Mickey Mouse. AIUI you would be able to reproduce Steamboat Willie verbatim, but if you attempt to publish a new work derived from Steamboat Willie that includes Mickey Mouse they may be able to stop you based on trademark protections.