I have a lot of problems with the FDA, both in terms of its scope and how poorly it tends to execute its duties (which it should be said is largely the result of an overly broad mandate and inadequate funding to fulfill it.) But setting aside the manifold institutional problems with the agency, it's kind of silly that tobacco has enjoyed the legal status of "non-drug" for the decades since we've all known better. So on its face, I don't really have a problem with giving the FDA authority to regulate it.
The manner in which the FDA is very likely to go about exercising this authority is going to be (with apologies to Dan Ariely) predictably irrational. Specifically, they are going to mandate lower nicotine content in cigarettes.
This is predicated on the (correct) assumption that nicotine is the ingredient responsible for initiating and reinforcing chronic use (I dislike the term "addiction"). In principle, this might make new smokers less likely to acquire a chronic habit.
However, it will almost certainly have a very different effect on the millions of people currently smoking: they will smoke more cigarettes, inhale more frequently and more deeply, and hold the smoke in their lungs longer. Manipulation of nicotine levels has been shown to have these effects in study after study: smokers modify their smoking behavior to maintain nicotine concentrations in their body. This goes both ways. What the strategy of mandating lower nicotine content ignores is that if you wanted to actually make a safer cigarette (a project that the public health establishment stubbornly and negligently refuses to contemplate), you would put more nicotine in it, not less, because then smokers will be exposed to much less of the tar, smoke, and ~4500 chemicals in cigarette smoke, all of which are more harmful than nicotine itself.
It's been argued that Phillip Morris is supporting FDA regulation because their market share will make them better positioned than their smaller competitors to deal with the impact of regulation on their business. This is almost certainly true. But I would also argue that they realize their best customers are about to get even better.