But the actual problem is that the city is super slow in building skyscrapers and rather tries to avoid them 'because they aren't Berlin's DNA'. Skyscrapers offer a much higher density and now is the time to really plan for a couple of them. They are just two new small skyscrapers planned for the next 5-10 years. But it's a very tedious process: everybody is fighting with each other, the city wants guarantees that the real estate funds build and operate schools and other public facilities in those districts, the funds don't want of course. Then there is the subway operator BVG which is kind of blackmailing the funds: They say that the skyscrapers are so heavy and they need money to stabilize the subway tunnels underneath. BTW, they do this with every bigger real estate project (recently with a huge mall).
In general, the city's council has a very good feeling about how to plan and build the city, they are really good compared to other cities. Infrastructure is great and you have many small city centers while Berlin-Mitte where the government resides is the busiest and most expensive one (no surprise). They are just lacking one important skill and this is managing large scale projects. Just an example: our new airport which was planned to open 2010 hasn't been opened yet. The new airport seems to be ready but doesn't get the approvals and it seems that it will never get the approvals and has to be shut down again (news from last week). Germany's general overregulation might also play in here. The city currently operates just two small airports.
However, they really need to plan proper skyscraper districts which seamlessly integrate with the rest of the city, complement Berlin's DNA and which should have also a good mix of business, leisure and living. So you don't face dead districts at night. The Potsdamer Platz which was created 20 years ago is an ok place which pairs all of those + two tiny skyscrapers.