Chapter 5 will debut on March 29th, and the abbreviated Chapter 6 will come out one week later on April 5th. The Chapter 4 problem set and revision will remain on schedule, being released on March 29th.
This switch will not affect the schedule of later releases. The 6th release will be on May 9th and will include revisions of Chapters 5 and 6 as well as the first version of Chapter 7 (basic regression). The 6th release will also include a problem set for Chapter 5 and possibly also Chapter 6.
Finally, we have tentatively scheduled the release of the 10 week coursebook (in PDF) for June 13th [May 28th update: this release has been rescheduled to the end of June]. This coursebook will be a PDF of all revised chapters 1-7 and problem sets for each.