Virginia Attorney General Ken Cuccinelli plans to sue the federal government if health-care reform passes. He doesn't explain the legal rationale he would use, but earlier he asserted that the bill under consideration would "violate the plain text of both the Ninth and Tenth Amendments." But this argument makes little sense. As the Supreme Court has noted, the Tenth Amendment simply states the "truism that all is retained which has not been surrendered." On its own, it doesn't do any work; it requires an additional argument about why the federal government lacks the power in question. And under current law, health-care reform is clearly constitutional. If the federal government can ban the non-commercial growing of marijuana for personal medical purposes, then the regulation of an actual economic activity like health insurance isn't even a close question. (And note that the appointment of Alito doesn't matter here -- O'Connor was one of the dissenters in Raich.)
Jon Chait, however, points to another reason to worry: "Nobody who recalls Bush v. Gore could completely rule out five Republican justices deciding on a wildly activist ruling on a high-stakes political fight." This is true insofar as it proves that it wouldn't be fear of being logically inconsistent that makes it unlikely that Scalia and Kennedy would stay their hand.
There is a big difference, though. Bush v. Gore was decided from a position of great political strength: The only two legislative bodies in a position to do anything about the ruling strongly supported the Court's actions. In this case, however, the White House and very possibly at least one house of Congress will be controlled by people who would be infuriated by an adverse decision, and unlike with an election, Congress would still be in a position to retaliate if it returned to unified Democratic control. It would be shocking if the Supreme Court were to announce a major doctrinal innovation in those circumstances.
Nothing is certain, but I think it's overwhelmingly likely that any suit alleging the unconstitutionality of health-care reform will fail.