This is a great question. I do not think we need to choose one or the other. As long as things are done well both will continue to grow. However, I do believe that things will get more competitive. Let me explain by way of examples.
First, J. Crew was only a online and catalogue company. It did very well and started opening up many store and they still do well. Therefore, they have two streams of income. Amazon.com is another possible example. They are a huge online presence, but now they are considering opening up physical stores. If they did so, I am sure that they would do well. They are so large that they can get good prices. Moreover, they have brand recognition.
Second, many traditional store are seeking online presence. All major stores and companies have an online presence. This trend will continue.
In conclusion, as long as the business model is good, both model will succeed. However, I would say that the biggest growth will probably be online.