That's a very good couple of questions. The answer is also a bit complicated (but exciting!).
We've just started the very early stages of working on a new game. We don't have anything offical to announce quite yet (and are a long way away from having a release date), but we're super excited to be working on something new. We're heading in a bit of a different direction with this concept as it's about puzzling out family trees and has more of a narrative focus (we're calling it an archival narrative puzzle game). We're delighted to get to stretch our dev brains once again as we work on the new game.
So what about Mini Metro?
Cross our hearts we aren't done with Mini Metro yet, but, because we are a pretty tiny team, the updates will be less frequent. The next few updates will include a few of the smaller features that have been frequently asked for, bug fixes (especially for that pesky passenger bug), and a couple of new maps too. After that, we shall see how things go. We will be balancing it out with the development of the new game, as well as all of the other business bits that studios need to handle too. Needless to say, we're in really busy times, but we're not done with Mini Metro quite yet.