The Department of Justice has filed its reply memorandum in support of its motion to dismiss in Sissel v. HHS, currently pending before Judge Leon at the United States District Court for the District of Columbia. You can access the brief here.
The current status of the lawsuit is that the United States has moved to dismiss the complaint under F.R.C.P. 12(b)(6), and briefing on that motion is now complete. As far as I know, Judge Leon has not set any time frame for his decision. Sissel's complaint makes the one claim common to all the ACA lawsuits: that the minimum essential coverage requirement exceeds Congress's enumerated powers. He further claims that section 1501 is not severable from the rest of the ACA, and thus that the court should declare the Act unconstitutional in toto.