Firmware 4.11 wasn't a mandatory update. If you have the new double-dipped Spiderman Blu-ray movies, your PS3 is required to have minimum firmware 4.11 or higher before it will let you play the movie. Firmware 4.20 also has "refreshed" Blu-ray encryption keys. I'll guess some new Blu-ray movies will require firmware 4.20 soon.
For some PS3 owners such as myself, I keep my launch PS3 with older firmware 3.15 before Sony started to lock down the firmware. Using as a Blu-ray movie player, having the newer firmware is not required. Then, I discovered last year, Pixar Cars 2 will not play on the older firmware. Now double-dipped Spiderman also will not play. All I'm saying is for some who want to keep their PS3 with much older firmware and use as movie player, not every Blu-ray movies will play anymore.
I don't know if the hackers community has figured out how to import latest Blu-ray movie encryption keys to function with older firmware. I know many just rip the Blu-ray movies to hard drive but I don't want to have terabytes of hard drives just to store movies. That is the reason physical media still has its purpose, low cost method to store the movies and legal.