According to what the current trends with auto manufacturers show, here is the order of introduction to the market of each technology (sorry, I don't have a crystal ball, so only the order, no dates):

Gasoline + electric hybrids (already in the market, phasing out IMHO)

Diesel + electric hybrids (may never see market, cost considerations).

Fuel-efficient, low-emmission Diesels (already in the market, strong in Europe (MB, BMW), here to stay a while - imagine 5-6 litres of gasoil per 100 KM in a 204 HP car - it's here!)

Plug-in electric (already here, but not to the ordinary man - the problem of charge life under load still very critical, autonomy menaced by long recharge times, and the non-existence of a re-charging network. High recharge times the major nuisance).

Fuel cell - electric (next big thing. However, not good until a big enough recharging network exists. The old problem of the egg and the chicken...).

Alternative fuels (already here, the bio-fuels are already a plague and a disgrace, increasing the cost of cereals, creating more famine on many areas due to higher cost of food, an incredible mis-useage of the soil - imagine planting to burn, not to feed!!! - I certainly hope this goes away quick, murderous to the Earth as it is - damn those idiot "ecologist"activists and their ignorance, preaching for "green fuel" and wanting it to come at the sake of human survival!)

The gasoline engine will disappear sooner or later, except for the use in Hybrids (hybrids still valid wherever there is an old network of gas staions, but not for electric or fuel cells).

This is my view.