DayZ won’t require Arma2 someday in the future.
The game is becoming a stand-alone title. Lead developer Dean Hall will stay as project lead, with Arma developer Bohemia Interactive publishing it.
According to Hall, the game will follow a model similar to Minecraft, coming with “fast iterations” and a “heavily discounted price” for a community alpha build.
However, people that bought Arma2 for the game shouldn’t feel cheated, the updates to the mod will continue to happen in parallel with the standalone title.