The white Xbox One LE wouldn't be a surprise at this point, lots of people like it. A BD-less version is also possible but it's too soon I think, maybe 2015 and only in partnership with cable companies. As for the big system update, not really a rumor at all. We've been hearing about it around the time talk about Windows 8.1 update 1 came out, they're suppose to come out around the same time. It's also been said that Aprils build conference is going to be big on WP8.1 and Xbox One. If you put all the pieces of info together then you figured a update would come around the time of build, they say March so if true it means that the software will be in place to take advantage of with new updated tools/SDKs at build time.
As far as the game rumors go, don't know but I expect some game news at build as well.