I'm waiting for franky to get a panic attack, and write 10 paragraphs on how Segwit does not improve anything.
SegWit or BU are only short term decisions and improvments. I'm sure that in long term Bitcoin will be replaced by the other leading crypto. You can resent, you can steam but Bitcoin is still number 1 because it has first movers advantage and a lot of speculation driving price up. As Google hasn't appeared in the first days of internet, the same is in crypto. Improved and sophisticated projects are underway. Differently from BTC they will have advantage to learn from their predecessors mistakes.
If you think of 'store of value' - only there is nothing better...
All other things you might think of could be build on top.