If allowed, yes.
But from recent indications, our present crop of devices might not be allowed to be imported or sold at all. Think Australia. Our beloved e-cigs are, at their core, unregulated and untested drug delivery devices. No one would approve those. They could be quickly and easily banned, without any need for new law.
Keep in mind, please, that the FDA does not have to PROVE anything. It is the manufacturers on whom the entire burden of proof falls. And the clinical trial? That's only Ruyan. No other manufacturer can benefit from those trial results. You see any other manufacturers funding clinical trials? Nope. They just want the quick buck before countries around the globe focus on this new addictive practice siphoning off some tobacco tax revenue.
What might be allowed, and would be taxed, are fully disposable -- and completely tamperproof -- e-cigs. Those can be regulated much better than liquids ranging from zero to 36mg of nicotine, coming from who-knows-where factories in China mostly.
If a best case scenario comes to pass, you might be able to walk into a drug store in the not too distant future and buy a pack of disposable e-cigs for about the price of a carton of tobacco cigarettes.
Less desirable? You need a doctor's prescription to buy them.
Least desirable? They are illegal in all forms because the liquid is both poisonous to children and pets and addictive to anyone vaporizing it, and the device's primary purpose is to deliver the addictive vapor to an addict.