I dunno, for me, although I wouldn't draw any direct connections between Pascal's "Rock and Roll" quote and Mark Ronsons hiring, I do think it (along with everything else we've seen since then) tips me further towards the notion that Amy Pascal was speaking deliberately and purposefully. 

That she didn't just misspeak, or respond sarcasticly, or even just use an off-hand metaphor etc. 

I still don't think she meant literal rock music, but I'm leaning towards her hinting at an overall artistic choice in the film that we are still not fully privy to. 

When I first heard the comment, I thought it meant something like "everything's ready to start."

However, now knowing that Greta has shifted the timeline, by the time we get to meet the Pevensies, it would be the 90s when grunge/alternative rock was at its height. I'm wondering if we might see a Susan who is obsessed with Nirvana/Kurt Cobain. Just a thought.  

Here's the Wikipedia page for the 1955 top-selling single records. I noticed, in reading this article, that until 1952, the top songs chart was based on sales of sheet music of the song, not recordings. Interesting.

This chart shows a lot of what I think of as my parents' music for most of it, but in October there arrived the iconic Rock Around The Clock.

https://en.wikipedia.org/wiki/List_of_UK_top-ten_singles_in_1955