Yes, Monzo won’t be paying interest on in-credit balances 
You should be able to save a lot more money by choosing the right provider for you though, than you will from that interest..
In the longer term, providers like Ratesetter, Zopa & Nutmeg etc. will integrate with Monzo, to enable users to easily manage those services from the Monzo app & earn money from their savings. You can start to get a sense of what that looks like, from this preview.