The Steam summer sale will begin June 25 and will end on 9 July. The news is not yet official, but is communicated by the developer of SteamDB, Pavel Djundik.
The same source also claims that Valve is going to integrate on Steam some new features including a rewards program loyalty. The initiative to which the Valve is reportedly working on is designed for regular customers and is based on loyalty points: you can earn by purchasing games from the store and will give the right to rewards of various kinds, including objects, prize, exclusive discounts and even full games. According to rumors on Steam will also be introduced to new reactions and to evaluate the user reviews.
As the developer of SteamDB is considered to be a source tends to be reliable, at present the information contained in the article should be considered as a simple rumor in the waiting of official communications.