Xbox is planning to release a brand new System Update for the Xbox 360 over the next few weeks. The update is being called the "Spring Update" and will contain improvements to features on the dashboard. The update will also be prepping the Xbox 360 for future enhancements, which are currently unknown.
According to a tweet from Major Nelson, the Xbox 360 will be receiving a new update later this week for a few members, everybody else will receive the update sometime next week. The update is required to connect to Xbox LIVE, as per usual.
The update includes some improvements to the Dashboard, Major Nelson refers to the update at the "Spring Update", and that the update includes "behind the scenes improvements". The update will also prep the console for future enhancements, these enhancements are currently unknown.