Does anyone know if there are plans for a steam release?

I would totally love to see a Steam release of Pico-8, it would just make it easier to reach a broader audience imo, its probably not on Steam because it just doesn't convince the developer.  

exactly the steam release can be really usefull cuz you can find guides to make some things that you dont know in the game creator

There is a listing for a Steam project that will play Pico-8 carts, but wouldn't be an actual port of Pico-8. It's called PEMSA and its listed as free, scheduled to be released Q1 2021 ... so I guess we'll see. They didn't exactly get a warm welcome from the Steam crowd.