I'm not sure why they think they can get away with this and keep subscribers. Instead of a July issue, Popular Photography sent out a "Special Double Summer Issue" for "July/August". Inside it says that they are now "published monthly (except combined January/February, March/April, and June/July issues)..." The Editor's Letter explains how much 'better' it is now that there are only 9 issues per year instead of 12.
While this issue is bigger than previous issues, it isn't twice as big. I am about half way into a "2 year (24 issue)" subscription, and they apparently decided to just short everyone some issues. I'm a long time subscriber, and generally like the magazine, but I'm not happy about this change. I will probably try to cancel my subscription and ask for a refund of the rest (which I probably won't get).