I really hope a Winter map is added, doing stuff like that makes the game more interesting.
After seeing the same map over and over again for hundreds of games, it can actually have a negative impact on the mood of players. Seeing something new like a Winter map would not only be really interesting and unique, but it would also make the game feel better to play when things get mixed up a bit. I'm not saying the current map is bad or anything, but It's just better to have something like that mixed up. Similar to how they did Butcher's Bridge for ARAM.