I like the idea of rolling release on Linux side

Small but stable updates that enhance user experience rather than waiting for annually updates. Apple should able to push kernel updates and features updates as individual updates that pushes to devices frequently.

This way could guarantees older phones are not left in cold (looking at iPhone 4) and devices could perform readonablely well.

Looking at current iOS developing model, Apple need to release big software release on one ear period, often we get an not well performed OS at beginning then starting to smooth out most bugs. If Apple are not confined with their annual updates schedule, then Apple could take the time they need to push new feathers while maintain usability and stability. User do not have to worry about app not being compatible with new OS.