I don't think Bitcoin will cause inflation in developing countries. That's more affected by other things, in particular how the country is being ran by the politicians.
That is the main thing how the politicians run the countries that are developing. Almost all of them are corrupt elites and loot billions out of the economy for their personal interest and this has been happening since long which has led the countries into nothingness. So there is already inflation and the common people do not even know what Bitcoin is because majority of them have banned the currency in the countries.
Many countries have adopted the Bitcoin especially the developed countries and going well with it, it has increased the economy rate due to its value and easy transactions system. We know that with valuable product we can earn a lot and especially in this modern world everyone is ready to accept the Bitcoin.
Recently Germany also realized that it is important for economy and therefore they recognized it which is good news for the Bitcoin and the people living in Germany.
Yes the trend of using bitcoin in developing countries is now increasing. I belong to an underdeveloped country and in my country i can see that most of the people are now taking interest in bitcoin, A few years before when i started investing money in bitcoin at that time no one was ready to invest their money in bitcoin, as they considered bitcoin as a scam, but now they have realized the importance of bitcoin and therefore they are now taking more interest in bitcoin to invest their money.