**Updates:**

* In June 2017, max capacity for items [was increased to 1500][1].
* In May 2018, max capacity for items [was increased to 2000][2].

Before, it was 1000. As others have also, I fully upgraded mine. Of course, I wouldn't be shocked if a future release allowed for further expansion.

I have included a screenshot of my 1000 each and what the store says about my Storage/Bag being fully upgraded.

[![enter image description here][3]][3] 


  [1]: https://twitter.com/PokemonGoApp/status/878038226191233028
  [2]: https://twitter.com/PokemonGoApp/status/996480700877504512
  [3]: https://i.sstatic.net/X8gUI.jpg