Salesforce core is Java. A smattering of other languages in the mix. I left Salesforce a year ago, their main developer productivity drains had nothing to do with the code base. It's their build process where it takes a minimum of a day to get code committed, even with their git on top of perforce hack which is seriously impressive, but still a process smell, that coupled with massive overhead from when dealing with inter team dependencies and various "edicts" getting passed down from on high that blow up any planning.

In short, you could have agents that code at 2x but it would have only a small impact on deliverabkes since non-coding processes have a higher impact on velocity.