Valve through its Dota 2 Twitter account, announced that the upcoming ranked matchmaking season will begin in January.
What are the Ranked Matchmaking Seasons?
The ranked matchmaking seasons represent the skill level a player achieves in a single season, as determined by their matchmaking rating and other hidden factors. Only available for ranked matches.
The medals are reset at the end of each six-month season. The medal of the previous season is shown next to the new medal for the next season.
To read more about ranked matchmaking seasons, click here.