Pricey, but possibly worth it: ICv2.com reports that Andrews McMeel plans to release a three-hardcover slipcased complete collection of Calvin & Hobbes sometime next year:

"This set will be similar to this year's two-hardcover slipcased Far Side collection which sold out very quickly, despite being approximately $130. Given the price on the Far Side package, it seems likely that the Calvin & Hobbes collection will be in the neighborhood of $200."