Could memristors be used to improve speculative execution?
Memristors are basically... memory. More specifically, memory that can sustain itself after poweroff. At a conceptual level, that's what Intel's Optane technology functions as.

Speculative execution happens all day, every day on every modern CPU you use. It's called a branch predictor. It starts executing code that may or may not actually be used going forward. If it is actually to be used, great, you haven't wasted a cycle. If it's the wrong branch, well, back it up and start over.

Why you're conflating these two ideas, I'm not quite sure.