FDA can't apply the UK model and regulate e-cigs as a medicine. They tried, but were sued by Soretta (NJOY manufacturer). FDA had tried to regulate using the Food Drug and Cosmetic Act, which they use to regulate nicotine patches, gum and drugs like Chantix. The court found that the e-cig manufacturers weren't marketing them as smoking cessation (i.e., therapeutic) products and that they therefore fell under the authority Congress granted in the Tobacco Act, after a landmark US Supreme Court decision called FDA vs Brown & Williamson. The ruling and injunction forbidding EPA to regulate e-cigs as medicinal compounds or devices was upheld by the appellate court and FDA chose not to appeal to SCOTUS.
However, it is unlikely that Congress and FDA won't eventually find some way to regulate e-cig products. After all, nicotine is an addictive substance, but it is still legal to grow, process, manufacture and sell tobacco products in the US. That is likely never going to change, so e-cigs and associated products aren't ever likely going to be banned, either.
There may be rules against sales to minors (which I support). There may be interim rules by state and local governments to make vaping in public places illegal (which I do not support). There may be federally recommended standards for quality control during the manufacture of the liquid and the devices used to vaporize them (hmmm). But an outright ban isn't gonna happen. It's infeasible.