Yes. The old WeatherLink Mobile App 1.0 will stay available for download and all existing users (those that registered their devices before the launch of WeatherLink.com 2.0) will be able to access and use during the whole period of migration (finalized in Q3/2018) and after that for an additional period of transition.
All new devices registered after the launch of WeatherLink.com 2.0 will be sending their data to the new mobile app that you can download in Apple Store and Google Play.