Is it likely that bitcoin will implement important changes in the future? Bitcoin is still the biggest cryptocurrency in terms of market cap, and it will always be the first one to solve some of the most fundamental problems around the implementation of a cryptographic coin. 

However we have many newer coins that solve some of the shortcomings of bitcoin and extend the possibilities: scalability/transaction rate, processing time, smart contracts, energy requirements, etc.

Because of this, I find it hard to believe that bitcoin in its present form would continue to be relevant (though I may be mistaken). I don't think that the miners would just let bitcoin fade out either though.

Is it likely that the bitcoin protocol will see very important changes in the future to address these issues so that it can remain relevant (block size, changes in consensus forming, block creation rate, smart contracts)? Are there technological impediments to this? Or is it more likely that this will be done in minoritarian hard forks, while the main bitcoin blockchain will go on essentially how it is right now?
many newer coins that solve some of the shortcomings of bitcoin and
  extend the possibilities


This is technically false; hence this question stems from wrong information.

If you can present a superior algorithm/protocol in your question(purely the explanation minus all buzzwords) community will consider it. Point is, if it exists out there, probably the core devs have considered it already. All the discussion is public w.r.t IRC logs so those might help understand shortcomings of various protocols that asker is arguing for.