bitcoin price will be around 4000-5000 USD per coin one day and that is already a couple of 100% rises and it will only happen slowly. i think something around 100% rise each year (give or take) is a good estimate of the future rises.
The thing with that is
BTCBTCBTC will lose it's purpose, at least when when it comes to doing microtransactions.
You mean due to the higher going price? If so, then I can't really agree with that. Bitcoin is a currency tool that you can divide into 100 million smaller units (satoshis). I think the transaction fees are the thing that will make Bitcoin less interesting for small transactions. Fact is that pools will depend on income through transaction fees more and more due to the halvings. And at some point, it will be their only income.