The Adobe Creative Suite receives regular updates from its creator, like most commercial software, and most of the time it's simple enhancements or security fixes. Updates are free with the purchase of the software and typically last for years after the software goes off of retail shelves. So when Adobe posted a security warning for Photoshop CS5 and proposed upgrading to the brand new CS6 as the only solution, they didn't win any friends from those who don't feel the need to buy brand new software.
To be fair, Adobe's security bulletin doesn't say that the security flaw will never be patched. But it does recommend "best security practices" for those who can't upgrade, or don't wish to. That rather implies that the company doesn't intend to fix the problem any time soon, if ever. Adobe classifies the security flaw as Critical, or in their words, "A vulnerability, which, if exploited would allow malicious native-code to execute, potentially without a user being aware."
Most paid software is expected to be supported well after the replacement is available, for stability and security if not for actual features. And with software as expensive as Photoshop (about $700 street for the standard version, $200 for an upgrade) sometimes even professional photographers and graphic designers wait through several versions before upgrading. The sky-high price of Photoshop is probably a large part of the reason that CS5 owners are already up in arms. Adobe has made no statement about the security patch thus far.