I'm anxiously awaiting the landing of https://wiki.mozilla.org/Electrolysis for years. That will be a major component of any improvement.
* Although we're currently running an A/B test to measure performance differences with e10s enabled and disabled, so you might fall into the disabled cohort when you run Dev Edition. This experiment is scheduled to end in a few days.
Nit: you mean (js-based) addons/extensions, not (binary) plugins.