Actually, removing RSS streams is what makes twitter a business. They hold the keys to the data and can charge customers for access to the firehose.

Your assumption is that the news consumption pattern ultimately dictates where the producers flock, which makes sense in the traditional journalistic business model. In a model where individual users contribute, the key factor is which platform gives users an easy way to speak (and I would argue that twitter has done a decent job at reducing the tweet friction)