I guess I just assumed that the new rule regarding groove technology would only affect wedges. But I have been told that many of the current iron sets on the market currently violate the new groove rule as it is currently written. If so, it could get prettty expensive for some, assuming they post a handicap or participate in any tournaments, being required to replace their irons soon for a conforming set at some point in time, not that the OEM's would mind. I would think that many would simply wait for the rule to go into affect prior to buying new irons, rather than spend the $ for a non conforming set of sticks they could only use briefly. Is this true?

Not sure, but isn't there a grace period until like 2024?

I think that you'd be surprised how many iron sets don't violate the new ruling. For example, I was told explicitly by Mizuno that the new irons are unaffected.

New groove rules kick in in 2010 for USGA and PGA professional events, and 2014 for USGA amateur competitions. For everything else, clubs manufactured before 1/1/2010 and conforming to the previous groove limit will be considered conforming until at least 2024.

For Titleist the AP2, Z Blend and Z Muscle currently have conforming "V" grooves and the AP1 has "Modified U grooves" (unsure if that's conforming)

Titleist Iron Features

Unless you are playing in professional tournaments, I wouldn't worry about it. You've got at least five and a half years as an amateur to conform and at least another 15+ years for everyone else to conform. Be honest, who will be playing the same gear in 5 years time anyway? By that time, just about every manufacturer will have it covered.