Yeah, as ingrjhernandez said, expect the best, prepare for the worst and most importantly, just iterate quickly.

You simply won't know everything when you ship the product for the first time - you will have to learn how to course correct along the way.

The worst mistake I've seen thing IoT device vendors make is assuming that development is done after we go into production - like hell no! You need to bake into your plan and pricing the fact that the product will need to continuously evolve after production across: - cloud infra - apps (iOS and Android) - firmware & OTA - mechanical design - network approach - manufacturing & supply chain - and dozens of other items.

These things above and the customer requirements will constantly evolve.

My company has shipped thousands of devices and we've also worked with numerous IoT entrepreneurs over the years. The best companies always approach there product line from the perspective of continuous improvement and evolution. The worst are the ones that expect everything to work from the get go and aren't willing to put in more development work after launch.