Microsoft has lost more than $1.2 billion so far on its Surface tablet business, an expensive experiment that makes tomorrow's revelations of new hardware an important milestone for the "devices" side of its corporate-refashioning strategy. On Tuesday, CEO Satya Nadella is expected to step on a New York stage and unveil one or more new Surface tablets, and outline his direction for the in-house hardware project birthed by his predecessor, Steve Ballmer.