According to a recent article published by Eurogamer, three separate sources have confirmed that GameCube games will be available for the Nintendo Switch's Virtual Console. These sources also confirmed that four GameCube titles are already in the works for the upcoming console.
The currently planned releases are Super Smash Bros. Melee, Super Mario Sunshine, Luigi's Mansion, and Animal Crossing, with the desire to keep Super Smash Bros. Melee easily playable cited as the reason for porting the 2001 title to the modern system. In addition to bringing Gamecube games to the Switch's Virtual Console, Nintendo is reported to also be internally discussing making the Wii U's GameCube controller adapter compatible with the Switch in some way.
Although the article does not specify whether these are the same sources that correctly reported the Switch's hybrid home/handheld nature to the site back in July, Eurogamer has thus far had a good track record in terms of reporting on Nintendo's upcoming console.