There was an article about the likely changes in the up-coming pensions bill on BBC's Working Lunch today. There's also some information about it here
The bad news is that the age for a UK state pension is going to increase from 65 to 68. No surprise there, since this has been predicted for some time. The good news is that the number of complete years of NI contributions required will decrease from 39 (women) and 44 (men) to 30.
I would have thought this is pretty significant for many people emmigrating. The question of whether to continue with voluntary NI contributions has been discussed before. If the target for a full pension decreases, this changes the equation considerably.
Of course, these are just proposals at the moment.