It is still in development, but because of a number of issues including pestering for release dates, beta vehicles being leaked and so on the developer has now taken all updates and development completely private.
As far as I'm aware London is still in progress, but the simple answer is "It will be done when its done, and when it is it will be released".
I know some people are impatient as it has been in development for quite a while now, but the simple fact is that creating maps for OMSI is very far from quick and easy. Route builders aren't magicians, and to get a realistic route/map working taken a tremendous amount of time, especially if your creating assets from scratch and working on a real life area, which by itself can create a whole new array of issues trying to recreate it within the limited set of parts in the game engine or making their own. I for one will be jumping to purchase it when it comes out, when it's ready ;-)
Have patience, it will arrive when it arrives...