ICORE has been considering a rule change to allow .22's, although I'm not sure if the rule change has been approved or not.
One of our local clubs has what is called a .22 action match, once a month. We shoot indoors so the weather is not a factor. The match is a cross between Icore, IDPA, and USPSA. We use IDPA targets, and scoring, but don't require the use of cover. Everyone starts from a low ready position, so holsters are not required. We allow rifles, revolvers and semi-auto pistols. I currently use my model 41, only because I haven't purchased a 10 shot, 4" model 617 yet. Much like steel challenge, the match is a bit of an eye opener for many people, because if your semi-auto (pistol or rifle) doesn't run 100%, you loose valuable time clearing jams, and quickly fall in the scoring. Since we do reloads "off the clock" the revolvers can be quite competitive with the semi-autos. I recently heard about a club in New Jersey that runs a USPSA 2 gun style match, using .22's. There, all reloads are on the clock, so loading the 10 shot revolver, even with a speed loader can be a bit of a challenge. Here you could use a 6 shot revolver which might reload a little quicker than the 10 shot version, but the extra reloads would probably be a disadvantage.
I personally believe that as ammunition prices continue to escalate, the shooting sports will need to make themselves more .22 friendly.