I would like it to happen because I will mod it in anyway, the game is 18+ and the usage of them would be optional and it fits the world quite nicely,, to be completly honest, I don't care at all if kids get bad influence by it, that's something that they and probably their parents should deal with. It may sound cold but why exactly should I care ??
Some parents are more open and don't care for ESRB ratings some are more protective and police everything, none of them are wrong, it just depends on individuals quite a lot.
Bethesda will end up doing the politicly correct thing and not let us smoke but bare in mind we are dealing with a game that has gory violence, chem injection, lying and betrayal, nucking entire settlements for no reason at all and poping psycho active pills left and right.
For the first person view they can use the minimalistic approach of Bioshock, just a sound clip (zippo opening, cigar burning) and a trail of smoke in air. I don't remember people go mad over that when Bioshock came out. ( Also you could harvest little girls in that so...
)