Kudos to ax, who pointed out a GameSpot report that Halo will be among the games demonstrated at Gamestock on March 12th. The relevant blurb for your reading pleasure:

Microsoft plans to unveil several new Xbox games at its upcoming Gamestock 2001 event in Seattle, Wash. Among the list of companies that are scheduled to show off new Xbox products are [snip]... Additionally, developers that have already announced Xbox games will also be on hand. Bungie Software will be showing the Xbox version of Halo [snip]...

As always, nothing is official until someone at Bungie makes it official, but this long predicted occurance could well be our first look at Halo in more than half a year.