My Points:
- BTC is tracable
- BTC is having a huge txn costs
- Time taken to transfer money is more than 10 minutes
- Mining is being done with somewhat centralized servers(pools)
- Several other Alts are now at the market and they performs well in the market
- People use different currencies for different purposes
Other currencies can certainly push BTC to be better and they already are. Bitcoin will always have an advantage because it came first and because of what it stands for. Bitcoin unlike many is not controlled by its developer.
In short, bitcoin can be replaced but it will take something revolutionary and for bitcoin to not try compete.