Under the most optimistic scenarion, the FDA will regulate ecigs as tobacco products. Here are my predictions. I know how lobbyists and government work and I've seen this movie before. In short, you can bet the farm on them.
No "non-tobacco" flavors (think of the children)
Sealed, tamper-proof cartomizers or cartridges.
No bulk nicotine sales.
Non-rebuildable atomizers. For ease of enforcement, possibly atomizers will be banned entirely and only cartomizers will be allowed.
Low nic. content, (my guess is probably max. in the 10-15mg. range)
"Designer" ecigs banned. Goodbye "Silver bullet", "screwdriver" and all the rest. The rationale will be that these items glamorize smoking and attract young people.
The PACT act will be amended to encompass e-cigs and delivery by mail or common carrier will be prohibited.
Only stores with permits to sell tobacco will be allowed to sell e-cigs.
Taxation will be imposed by Congress as well as the State Legislators with the help of the BT lobbyists who helped so much in diverting 50% of the billions in revenue from pre-packaged analogs to the tiny (approx 0.5 mil. consumers) bulk RYO/MYO market, resulting in a 2000% tax increase. The goal will be to replace any lost revenue on a 1:1 basis and ensure that it is at least as expensive to vape as it is to smoke an equivalent number of analogs. The BT lobbyists refer to this as "leveling the playing field", it was the goal when setting the tax rate on bulk tobacco and, by-and-large, it was achieved. When joined by the health nazis, BT will have an even easier time of it this go 'round.
Due to the recent "Citizens United" court case, (which allows unlimited political spending by any corporation, foreign or domestic), any politician who dares to object to the taxation level or any other restriction put forth by the army of BT lobbyists, will find themselves faced with a very well funded opponent and a media blitz of negative advertising during the next campaign cycle. Politicians know this, so they will shut up and pass legislation to tax ecigs at an equivalent rate as they have other forms of tobacco.
Ultimately, an attack by BT, the FDA (supported by Pharma) and the smoking Nazis, along with scared and revenue starved State and Federal legislators, will be launched to make ecigs expensive, inconvenient, and unappealing. But they'll be doing it for the children, so it'll be fine.