According to a new post added to the PlayerUnknown's Battlegrounds Steam community page today, the developers currently have a roadmap for improvements in the works, which includes a new map to be added in the first half of 2018. Below is a snippet from the post in which they make it clear that plans are not just in the works but seem to be beyond planning phases, but according to the language they use, it appears the third map will make an appearance before the end of June. If I were a betting man, I'd say the best time to reveal it would probably be at E3 for a launch the weekend after the event, but we shall see.
Early this year, development of some of the major features and systems was delayed as our focus shifted towards tightening our anti-cheat effort. Also, due to other reasons, we have not been able to show you the team's development roadmap for 2018. We would like to ask for our players' generous understanding that despite the team's eagerness to share what we have been planning and working on, the timing had to be changed. We do have a lot of exciting things that we want to share with you, including new content to provide more extensive battle royale experiences as well as improvements and modifications to create a deeper and more realistic gameplay. In March, the team will reveal what you can expect from us in the first half of 2018 in terms of our development and new content plans which, by the way, include a new map.
The current test server patch is mostly aimed at further optimizing the gameplay and fixing several significant bugs. More optimizations and fixes are being worked on and will be shared with you when they are ready. Please refer to the patch notes below for details and leave any feedback you may have on our forum.