everything needs improvement and developments with the passing time so is the case with Bitcoin. I am not saying that it is not standing at a stable or secure position, no doubt is it has touched the many steps of development and working as the king in crypt market. But development with time will bring more improvements and it will become more efficient.
Especially if we are speaking about IT sphere - if you do not evolve/adjust/update/improve as the time goes by, it means the project is dead. Do we have things to improve? Of course, now LN is the most important element of the development, as we learnt in Dec 2017, that BTC transaction could take even 24 within its blockchain. Other features can be taken from other cryptos, like ETH (contracts, dapps).
The only feature which would be potentially harmful for BTC would be full privacy (like of privacy coins), as this would automatically cause a hostility from authorities and could lead to bans for BTC (as officials are too afraid of any sort of possibility allowing money laundering).