According to http://www.myannuityadviser.co.uk/, an income drawdown facility will let me draw an income from my pension fund while leaving it invested. Does anyone know if this law is going to change in the next few years?

I don't know about the "law" changing, but the rules governing pensions can be changed at the drop of a hat and have been recently. On 6 April 2011 the Government restricted income drawdown schemes, reducing the annual amount that could be drawn in line with annuity rates set by the Government Actuaries Department (GAD) which led to a significant reduction in income for most people. I think it would be safest to assume that there is no certainty at all that the current rules will not be tampered with again and again.

As you are probably aware, there is a difference between "income drawdown" schemes and "flexible drawdown", the latter allowing individuals with existing guaranteed annuity income over £20k to draw whatever they like from their pensions, up to and including the whole amount if required. I am in the happy position of qualifying for flexible drawdown but at the first sign of Government interference, I shall draw down the lot.