Are there any plans for a sequel to Nancy Farmer's The House of the Scorpion?

Answer 1

The House of the Scorpion (2002)
Remember Me - Firebirds: An Anthology of Original Fantasy and Science Fiction (2003)
The Sea of Trolls (2004)
A Christmas Carol by Charles Dickens and Nancy Farmer (2004)
Full-Blooded Fantasy: 8 Spellbinding Tales Where Anything Is Possible (2005)
Clever Ali (2006)

Those are her books that she has published since the one you've mentioned. Her next book is a sequel to Clever Ali.