There is currently no outstanding work on improving performance on low-end systems. Investigating exactly what would be the target for improvements would take significant engineer time and effort, even before any investigation on if it is possible to speed up those systems is performed.
That is not to say that there won't be some PR that appears tomorrow that removes some massive bottleneck, but that is extremely unlikely. As far as I'm aware, none of the current active devs have any active interest in performance of such old systems. The cost/benefit ratio just doesn't add up and doesn't seem to align with their personal interests (Remember - dolphin devs are *volunteers* - so it's natural they'll do what they're interested in, as they're doing it for *fun*!)
Any performance changes on such a system will more likely be accidental, if measurable.
That is not to say that there won't be some PR that appears tomorrow that removes some massive bottleneck, but that is extremely unlikely. As far as I'm aware, none of the current active devs have any active interest in performance of such old systems. The cost/benefit ratio just doesn't add up and doesn't seem to align with their personal interests (Remember - dolphin devs are *volunteers* - so it's natural they'll do what they're interested in, as they're doing it for *fun*!)
Any performance changes on such a system will more likely be accidental, if measurable.