Nope. Won't happen. The tobacco companies will see to it. They'll make sure that e-cig taxes are raised to eliminate any real cost advantage for anyone who doesn't DIY. And many people will never DIY.
That's exactly what they did to the RYO market. With the premade, filtered tubes and the injector machines, RYO was becoming more and more popular. It was cheap and easy. The tobacco was better than what was in the prerolled cigs and the finished product was nearly indistinguishable from a prerolled cig. It wasn't your grandpa's roll your own.
The tobacco companies were threatened by this. You could roll a pack of better cigarettes than they could sell and your cost was about $0.70-1.00/pack or less. So, what did they do? They arm twisted Congress to jack the taxes up from about $1.25 to $24.00 per pound of loose tobacco. They had Congress impose a huge tax on rolling paper and pre-made tubes. The cost of a pack of RYO doubled or tripled. Only the exemption for pipe tobacco provided some relief, but they're working on that right now and, eventually, they'll close that loophole too.
If you don't think BP will do the exact same thing to e-cigs and juice, through both taxation and regulation, you haven't been paying attention. Ecigs will take a bite out of cigarette sales, but they wont make them obsolete. Big corporations call the shots in this country and the tobacco companies will not allow that to happen.
Unless BP controls the entire e-cig market, can eliminate DIY juice, and can charge whatever they want, cigarettes will be more profitable to them than e-cigs. Lorillard bought Blu, but their beancounters would much prefer you stuck with Newports for the next 30 years.
Since e-cigs have been declared a tobacco product, they cannot and will not be banned. Years ago, as part of the Master Settlement Agreement between the gov't and the tobacco companies, the FDA was given sole regulatory authority over tobacco products. Part of the agreement was that the FDA or Congress could not ban tobacco products or impose a de-facto ban, (by regulating nicotine to 0.01% for example). So now, when something is declared by the court to be a tobacco product, it faces a double-edged sword. It is protected from an outright ban, but it can be heavily regulated.
Making cigarettes, or any tobacco product, illegal in the U.S. is out of the question. That is a settled legal issue. The government is expressly prohibited from banning anything declared by the courts to be a tobacco product. They can regulate the hell out of it through the FDA, but they cannot ban it. The tobacco companies saw to that as well.