I think (and hope) that it won't be a subscription model....
IMO, it will be more a multiple possibilities fee upgrade following what you want to unlock (morph, FXs, FXs number slot, Profiling....). But paid once to justify & reduce the possibilities/price gap with head/rack/stage .
I don't totally agree with this but can understand it.
It could/would be cool if the price tag would be lower for big units owners like L6 does with Helix Native following the unit you have....
Sure, don't get me wrong: i can understand it as well; it's how things works and makes way more sense than buying an unit and expecting free upgrades for the coming ten years.