There may be an increase in Steam deals very soon with Valve's decision to give developers greater control over sales. Though not yet fully functional, developers will not only be able to decide when to have a sale, but also how much less gamers will have to pay.
In the past, sales were controlled by Valve. They decided on the time a sale began, how long it lasted, and so forth. But now game creators can set a sale on a whim, set a price, and even choose to participate in the weekly Steam sales. The only limit on this new feature appears to be that a custom sale will last no longer than two weeks.
Though a set date for this implementation is not known, it hopefully won't be too long before gamers can fill their library with even more great quality games for cheap.