Earlier quoted context omitted.
Your device will keep working yet, but what if you switch phones/tablets? Now you need to setup a new device with the watch and...oh wait... Pebble re-downloads and re-installs all the apps. If their app/servers go away, now we'll be looking up hack people wrote on github to get our devices working again.
Yeah, fortunately TiBu can backup both the Pebble app and the Bluetooth pairing. But that's basically next, modified firmwares already exist I believe, so I don't think it's unreasonable to think that if we need to use those and sideload apps we'll be able to. I'm fairly sure that I could crack the pebble apk myself to remove the authentication stuff at the beginning if it's needed. Backing up all the apps and stuff…
I don't think PBW format has any magic in it that could enforce cloud dependency.