I have a theory on what will happen and why. Obamacare will be struck down in toto. I believe that the conservatives on the court did not agree to take on this case at this time — they could have waited — if they did not believe they had the 5 votes to strike it down. I think they had the 5 votes from the get-go. So, they were ready to take it on. Also, if they waited and the law was implemented and Obama re-elected and another justice retired, they would never have the 5 votes. Just a theory, of course. I have no evidence or source to back this up.
They can't know what votes they have before there are arguments and briefs and debate. They took the case because it was there. They could have taken it earlier and chose not to.
I predict a 5-4 or 6-3 ruling striking down the mandate and certain other provisions that are directly tied to the mandate. The entire law will not be struck. Their biggest problem is going to be figuring out how to draw the line, but they'll come up with something. As some of the justices pointed out, many of the provisions in the 2700 pages are routine functions, and it even includes some annual appropriations that would have been passed on their own. They aren't going to strike all that.