Just some random thoughts.
There won't be any "official" data on this - who is doing currency surveys in this business? It's just pretty obvious looking around. There is however plenty of data on the CAA website showing that each year about 100x more people get an IMCR than an IR (NON commercial).
The CAA have really good data on licence/rating lapsing but they don't publish it. If I was them, I wouldn't publish it either.
An FAA IR needs to have done 6 approaches in the past 6 months, to fly under IFR. That means you have to be doing more than that, of course, otherwise the oldest approach you did will be just about to "drop off the end". You've got to be doing something IFR every fortnight, more or less.
A JAA IR has to sit a checkride every year, but he may not have flown for a whole year before that. Is that better? We could argue about that but I don't think it is better. We all know the examiner won't fail you unless you do something pretty bad.
The biggest enemy of all this is lack of currency... currency costs serious money, and decent planes cost even more money, and money is in a very short supply in this business. Just look around your local airfield.
If the IMCR is abolished, we will still have every "instrument capable" pilot flying in cloud en-route, just like they do abroad at present. One just can't do an IAP and one can't depart from a towered field if it's sub-VFR. A very poor case for safety! I am 100% certain that nobody would have the ba11s today to introduce the IMCR (the IR training business would be up in arms about it, wouldn't they, Slim-Slag?) but equally I don't believe it will be abolished. Not until there is an accessible "IR" and probably a comprehensive airspace review to something like the US model.