The Supreme Court will take to the bench at 10am. It is possible that they will announce their decision on the Affordable Care Act shortly thereafter, although I am hearing that Thursday is more likely. You can find out quickly by opening a window for SCOTUSBlog and then launching their live chat module. The way they do this is that the cases are announced by reverse-seniority, meaning that if any decision was written by Elena Kagan, it will be announced first. Then Sotomayor, etc… Chief Justice Roberts is considered to have the most seniority even though he’s relatively new to the Court.
The Affordable Care Act decision could be written by anyone. If Chief Justice Roberts is in the majority, he gets to decide who will write it. If he is in the minority, then the most senior Justice in the majority gets to decide. If Roberts joined with Kennedy to uphold the law, he probably wrote the decision himself. If he joined Kennedy to strike it down, he probably let Kennedy write it. If Kennedy split from Roberts to uphold the law, he also probably wrote the decision himself. So, the most likely authors are Roberts or Kennedy, which means we won’t hear the decision first.