As we mentioned in September, there are a number of features in the works for Dota 2 that we’re really excited to share with you. Among them is a major improvement to Dota 2’s engine that we are aiming to release in the first half of next year. One of the main features in this engine improvement will be the ability to rapidly create entirely new game modes. You’ve seen some of this work with the Dota 2 Workshop Tools Alpha that began earlier this year. In the past, our Diretide and Frostivus updates contained game modes that were very time consuming to build and maintain, and would need to be rebuilt from the ground up after the release of the engine update.
With Diretide this year, we decided that it didn’t make sense to build another one of those resource-intensive game modes, for two reasons. The first was that the mode would quickly become obsolete when the engine changes arrive, and the second was that building it would have taken resources away from the work that needed to be done to ship the engine change itself. Now that Frostivus is on the horizon, we find ourselves facing a similar choice and, after some thought, we believe that once again the right choice is to not develop a Frostivus game mode.
This doesn’t mean that you won’t see interesting updates from us before the engine improvement goes out next year. We are already hard at work on our next major update, the New Bloom Festival in February, although we will continue to avoid building new game modes until the engine improvements come along.
Source: Dota 2 Official Blog