
Valve announced that they will split the Dota 2 game in two, into a test version and another version with more stability.
Both versions will still be updated each week, but the test version will be one week ahead in new content and features.

As a result of this, both versions of the game will be getting updated each week. If you want to help test the new content, or just try it out ahead of time, you can play on “Dota 2 Test”. If you are more interested in stability and don’t mind being a week behind on new content and features, then you can keep playing Dota 2 as normal.
Unfortunately, the switch from previous update process to this one has been a little tricky, as we get the back end set up for Test, so there’ll be no update today. We still hope to have an update ready in the next few days.
Source: Dota2.com