Subscriptions are coming I bet. The whole ui.com account thing where they force you to create an account and link new devices like the UDM Pro are the writing on the wall IMO. They back-peddled on adding it to the v2 firmware of Cloud Key's IIRC, but the end game is likely to get everyone paying per device per month.
The last time they had a pay per device per month service it started at $1/device/month and then they bumped it to $10/device/month. Somehow they thought the one time cost of a device should become an annual cost and that people would adopt it. Obviously that flopped.
Now think of the same scenario, but everyone's gotten complacent and are getting dependent on their devices that are linked back to ui.com. They might not blatantly flip the switch, but now that they have a hook for licensing checks they can start shifting development so new features are licensed for a monthly fee rather than getting them free forever when you buy a device.
IMO as soon as the all-in-one devices that perform management (ex: UDM Pro) while being linked to a ui.com account get enough adoption they'll shift to some kind of feature licensing or simply release new devices / revisions that require "cloud licensing" or something similar.
They're also very flippant when it comes to breaking devices in a way that prevents a connection to the controller. They think SSHing into broken devices to fix them is reasonable and it's not if you have to deal with many sites / devices.
Its gotten much much better over the last six months or so. The transition to generic linux for their router line was rough, but the worst seems to be over.
