With all the 3rd party apps, such as WeChat (China-based), Kakao Talk (Korea), LINE (Japan) and many others, I'm not surprised that it's affecting mobile networks' sales of text messages and calls. But if Android 4.4 will include a free messaging feature on Hangouts, it's possible that mobile network providers would have to change their business model due to less revenue from text messages and calls. More info can be found here
The article also discusses how the number of people using Android phones make this a definite threat to mobile networks, plus the existence of more free WiFi spots over time. I know that instead of buying phone credits from our mobile network provider, my relatives have started downloading free messaging applications to communicate with friends and other relatives who live in other countries. Do you use any of these messaging apps?