The big problem with a plug-in hybrid is the plug-in part of the equation. Where they make the most sense is in cities and the suburbs surrounding them.

In the UK and Europe the vast majority of people living in cities and suburbs only have access to on street parking. There will therefore need to be a huge investment in infrastructure to wire up kurbside charging points and you'll need to somehow figure out a way of metering each car, reading that meter automatically and charging the owner / driver for its use.

Furthermore the vast majority of people won't buy the cars until you have all the infrastructure in place for them to be able to charge them up at the roadside so you have to incur a huge amount of cost putting the infrastructure in place and yet get no return on that whilst you are building the infrastructure.

That is why hydrogen fuel cells are the future - the infrastructure is far cheaper and, importantly, quicker to put in place as you only need to upgrade existing petrol stations to be able to store hydrogen tanks and refuel hydrogen cars. Furthermore you can start off relatively small with, say, only the one pump dishing out hydrogen and a small tank and increase it as and when the tech takes off.

Compare the costs of this to the costs of running power cables to every kurbside parking point in city centres and suburbs and it is a no-brainer.