While its true the future cannot be predicted, you can make some reasonably sensible assumptions.
Energy suppliers need to fund and roll out smart-metering, this needs to be in place by 2020, in addition they need to fund and roll out a smart-grid by 2050, from the latest infoamtion I remember reading (so it's probably entirely inaccurate now). The government are not supporting suppliers in terms of funding.
In addition suppliers have rather hefty Carbon Emission Reduction Targets (CERT) that will also require considerable funding, and this is on top of the work that is being done to increase the renewable energy portfolio of the UK and replacing ageing power stations.
Ofgem has published their findings on the energy market in its current state, and given the current economic downturn has established that in any of the possible scenarios whereby suppliers meet their obligations (as mentioned above) an increase in consumper cost is required although the increases range from 15% to 60%
The current energy market has seen two new suppliers enter the fray Ovu and First Utility and both have jumped into the mix by cutting thier energy prices to make them (at various points and maynot be so at the time of writing this) the cheapest energy provider in the UK.
What does all this tell us? well from my perspective (I work in the energy market but do not hear about price changes until the general public do) I think we'll see prices continue to fall in small increments as any of the 'big six' try to reasert themselves at the top of the market, and the new guys continue to try to beat them to icnrease their market share. These decreases will however in my opinion be relativley shortlived as the pressure to invest and meet their commitments increases.
The advice i'm giving to our customers is to take advantage of the best prices available (generally online tarriffs), weigh up the cost saving versus any cancellation fee's you may have to pay for leaving them early (for example a £400.00 pa. saving versus a £30.00 cancellation fee). Then keep an ear out for price increase alerts and consider switching to a Fixed/Capped/Protected price at point.