Hello, yes! the unstable versions are also on Steam. You just have to opt into the "testing" beta channel: Right click on the game in your library -> Properties -> Betas tab -> then select the "testing" option in the drop down, this will queue up the update for 0.52. 

BIG NOTE:  they're labelled unstable for a reason ;)   Playing certain saves in 0.52 will prevent them from working in 0.51 or an older version of the game anymore.  But 0.52 is almost done and will hopefully be promoted to stable in the next few days hopefully 🤞