There are now about 8m smokers still in the UK and 1m e-cigarette users. Over time, the number of e-cigarette users will increase and overtake the number of smokers, as former smokers realise they can service their nicotine addiction at less risk to their health and less cost to their purse. It might take 50 years or more before this happens but by 2100 at least, I expect real tobacco smokers to be in a minority to e-cigarette users, at least in the UK.
E cigarettes aren't the answer. A full on quit IS the answer, sad thing is if everyone quit smoking, the government would want the tax to be made up elsewhere.