will be called Bitcoin - or resemble Bitcoin v0.1
I edited my post a bit to clarify while you were writing your response.
I do indeed view "Bitcoin" as a tree with many branches, some of which give up fundamental aspects of monetary soundness and will imo be pruned / fall away by the action of the market, as most will.
Some may deliver good and necessary improvements or vital course corrections (like massive on chain scaling pursued in the Bitcoin Cash branch). Such branches may come to replace the main branch over time by gaining the value and most-proof-of-work-put-in over time.
This is where the branch analogy probably breaks down and these so-called "altcoins" can be like seeds that can carry and sprout to bring peer to peer electronic cash to people, even if what the masses know as "Bitcoin" dies. Which is not to say it will -- it might linger around longer than any of us will ever experience.
future world reserve currency like we have now with the dollar?
Sorry to say this, but this pre-supposes a world with power structures like we have them today. Around us the old order is crumbling like a dam with holes, about to break.
I believe with sound money as introduced by the Bitcoin idea our human civilization has a chance to take a very different trajectory, one that might not require such a "world reserve currency". But perhaps one will arise naturally in the form of the dominant cryptocurrency of the day.