One advantage Bitcoin already has over m-pesa is that Bitcoin is an international currency, whereas m-pesa is confined to East Africa. This means that people in developing countries that sell their goods or services for Bitcoin have access to a currency limited, yet fully international market.
Or, why not both?
From what I have seen some of the main advantages of mobile banking are: 1. You can manage your account with any phone. Most people here just use gsm phones.
2. Opening an actual bank account is expensive. Not expensive from my western point of view. But from the perspective of local people it is.
3. It is easy. Mobile carriers are everywhere. And since cash is still the way of handling most money transfers it is very convenient to be able to, even when you are in a village in the middle of nowhere. Go to a place with the "airtel money" sign and get cash so that you can buy that roasted cassava.
And a lot of the early failures of Bitcoin in developing countries were the result of overzealous Bitcoin supporters rushing into a developing country with no prior experience, and then running into some of the inevitable problems (e.g., no reliable electricity).
If it's going to work in these situations, it's going to have to happen from within, not imported by outsiders.