No mention of Colosseum, and we checked, it didn't shadowdrop.
http://www.nintendoworldreport.com/news/74522/nintendo-classics-gamecube-to-get-pokemon-xd-in-march
We have a window for half of the Shadow Pokemon series for the GameCube Nintendo Classics, but probably not the one you thought.
A trailer for Pokemon XD: Gale of Darkness (2005) was shown during the Pokemon Presents today with an announcement of a March release window. It covered most of the plot as well as the battle with box mascot "XD001" Lugia.
XD was announced for addition into the GameCube library alongside its predecessor, Pokemon Colosseum, in the Switch 2 unveil Direct last April: no details were given on a potential Colosseum window.