I'm don't think satoshi planned for the 1mb size to be immutable.
What satoshi said doesn't mean what satoshi knew. He may or not have known that 1 MB blocksize would eventually become yet another value which becomes immutable due protocol maturation
A remarkable fact about Satoshi (which is all too often forgotten) is recorded right here on Bitcointalk: sometimes, he got even fairly significant things wrong
Even more remarkable: Satoshi was happy to be wrong, because he wanted to get Bitcoin right. He wasn't jealously guarding the design decisions made in the original Bitcoin 0.1, it was the complete opposite. He fully welcomed and encouraged others to poke holes in Bitcoin, to make it as good as possible.
What would he think now? Who knows (we may never hear from him/them again). We've got to get this right now, not him, and that appears to be exactly what he wanted.
I believe Satoshi would say that the Core developers are on the right path. It's clearly the fee market structure that's what will make everything stick together.