The Migration Advisory Committee is a theoretically independent unit of the government that provides ministerial research. They came out today with a report that concluded that a minimum income of somewhere between GBP 18,600 and 25,700 was a good number to use.
They pointed out that using those numbers could reduce family immigration by 45 - 63% (which is the central platform of the coalition government currently running the show).
What happens next? Well, it needs to go to a Parliamentary committee who will take oral and written evidence from various experts. After that it will be sent to the drafters who will hammer it into a bill, and then the bill will be laid before Parliament. Then it gets three readings in each house and blah blah blah blah.
The whole process usually takes a long time, and thus won't affect anybody in the pipeline. This is about entry clearance and not ILR or LTR.
*BUT* if you were planning to apply sometime in 2012, and especially after April 2012, and your income is below GBP 18K then you *might* be well advised to consider your options for acceleration. Note that I didn't write that you *have* to accelerate; but rather that you should consider it...