Personally, I hope ST build something similar to Rule Machine or maybe if it comes back allow offline mode, not even sure if thats possible.
Feels like Cloud should be something optional or least work without it fully, so local processing should come first. I think current ST apps already work offline? Not sure current hardware could allow vast amounts of offline apps etc but maybe a later version can.
I think SmartThings could serve as a simple proxy for anyone wanting online access, they can still log events/collect stats e.g average device ownership, which devices/apps are popular, data mining etc.
Right now not sure I'd be willing to pay a monthly fee but if everything could work offline first sure I'd consider a small fee (probably based on device count) so I could communicate over the internet, just don't like the idea of rules/functionality breaking because either ST has gone down or you no longer have internet access for some reason.
What you also have consider is every powered device adds to the electricity cost. Right now for me it only adds £1 per month having all the bulbs/devices on standby, this might improve in future devices with lower standby costs hopefully! I could easily see that increasing to £5 month or even more for some users.