I rarely see prices for Mizuno clubs drop when a new line of irons come out. For what ever reason they don't seem to make sharp discounts like the other OEM's. My first set of Mizuno irons were the T-Zoid, when they came out with the T-Zoid Pro I was expecting a price drop on the T-Zoid but never saw it.
When I bought my second set, I debated between the MP62 and MP67, finally went with the MP62. Just last year I was getting a set of MP68, I actually found two different stores that still had new sets of MP67 but they were at the orginal price, so I went with the MP68.