Just because Sony wrote a EULA that covers their own butt (in every conceivable situation they could think of), does not mean that it will be legally upheld in court.
You need to consider when you agreed to that EULA. Was it before you purchased (and opened PS3, and used the PS3)? No, it was afterward.
Did you purchase the PS3 system based on Sony's advertised features? Yes.
Does a manufacturer have the right (regardless of the manufacturers claims) to retroactively alter the product to remove advertised features? Courts will decide this, not the manufacturer ...
Product manufacturers would love to take your money and then retroactively do what is in their own best interest. This is why there are consumer rights, and there are courts to uphold those rights.
Normally, product manufacturers do not go down this path. But, Sony chose to do so. EULAs like this are rarely challenged in court.
No questions asked, this is new ground. And could set a very scary precedent *if* Sony is allowed to disable advertised features as they choose. It will redefine the concept of 'purchased property'.
No matter how you look at it, Sony is removing advertised features ...
Choose to loose either ...
A) Other OS
B) Network access, online play, to-be-released game titles, BluRay compatibility
If Sony didn't purposefully prevent you from playing to-be-released game titles (by checking the OS version), then they may have more room to legally withhold online play and 'feature updates'.
BUT forcing users to update (by requiring the OS update, in order to continue using the PS3 system for to-be-released game titles) is the crux of the issue.