You can't recreate Skyrim with a different engine and expect the exact same experience that just runs better. It would be a fundamentally different game. Suddenly, the game runs at 30 fps constantly, but at what cost? Whose to say the experience feels familiar, or is enjoyable? Maybe it's not even fun anymore.
My point is, the programming that Bethesa uses to tie the worlds of Morrowind, Cyrodiil, the Capital Wastes, and Skyrim together is an excellent system that doesn't play nice with the way the PS3 splits its memory. Bethesda released the best product they could in the time given to themselves, knowing full well they would have a long road of patches and optimizing ahead of them. I don't fault them for doing their best. Their PR svcks, their communication with fans and consumers svcks, and I would have loved a game that runs at 30 fps constantly.
It's not the PS3's fault - the splitting of its memory allows for fantastic game experiences using very specific programming (see: Uncharted). It's not Betheda's fault - their engine works wonders but depends on a certain amount of available memory. In the end, the situation just svcks. If you're currently dealing with unplayable lag, I wish you the best. Optimizations and fixes are coming, but if your save file is already gargantuan, there's only so much that changes can do for you with all the values and references the game has indexed for you. For others, their save files were manageable size (4-8) prior to the most recent patch, and further patches will be more noticeable for them. For those starting a new game, enjoy the experience - the current state of the game, and Bethesda's plans for updates, will give you an incredible experience for a very long time to come.
Its not bethesdas fault? They did not make allowances for how the ps3 handles memory. I'm guessing since they're developers and have made games for the ps3 before they should know how the ps3 handles memory.