Everything is subjected to this world into work will become obsolete , but here why you are not thinking that this is technology not the living thing that it will lost its quality by time to time .
Just see toward the android platfrom , in the very starting android was not better at his place and was much comparable with Java programming , but time to time android version get updated and finally it become a most perfect programming for the development of application instead of another java etc .
So here this is Blockchain technology not any living thing , and also you can see that time to time hard fork in Bitcoin network making the Bitcoin experiment to make it much better and also for increasing speed they are doing new new experiment ( segwit wallet introduction and 2M block to double to make transaction more faster with less fees ) .
So here big big banks knows very well that how much it is better to have Blockchain Technology in banking sector and how they can grow the industry of the banking system time to time with new new implementation of techniques in Blockchain technology .