Might and Magic X was the prospective tenth installment in the Might and Magic RPGs series. At the time of 3DO's bankruptcy and dissolution in 2003, it had only existed "on paper" in an early planning stage, with early elements of its design planned by Might and Magic IX designer Tim Lang. The game was to be set in Beldonia, and was planned to feature Nicolai Ironfist and the Jarls of Might and Magic IX. It did not enter production.
Upon obtaining rights to the series, Ubisoft, despite continuing the Heroes of Might and Magic spinoff arc, did not show any clear intention to extend the original series. However, long-time fans held the belief that Ubisoft would eventually decide to work on the project. 
In 2009, Ubisoft's Might and Magic producers (presumably Erwan Le Breton and Romain du Waubert) offered closure on the subject, stating Ubisoft would never create Might and Magic X, in accordance with their new branding policy. They did not, however, rule out the possibility of creating an RPG in the future.
A group of developers picked up the intention to create Might and Magic X and worked on it for a couple of years as an open-source fan project. The project died at the end of 2012.