Two interesting numbers for discussions revolving around the future of SMS and traditional mobile voice telephony:
In 2011, 55 billion SMS messages were sent in Germany (population 82 million), up from 41 billion messages the year before. That's a stunning 30% increase! Not exactly a downward trend from a quantitative point of view, despite the growing competition from mobile instant messaging services.
Traditional mobile voice telephony is also not on the decline, despite the ever growing number of non-voice communication methods. In the course of 2011, 107 billion outgoing voice minutes were logged in Germany, up from 102 billion a year earlier. That compares to 191 billion outgoing voice minutes over fixed line networks (down from 195 billion minutes the year before).
For details have a look here and here (sorry, both sources in German)