things such as smart contracts and decentralized exchanges and side-chains are additional or bonus things that can be added to bitcoin anytime there is a demand for it. and so far there really has not been any demand for smart contracts expect for ICO scamming, no demand for decentralized exchanges because people prefer the options centralized ones offer and side-chains are not favorable over on-chain transactions.
but each of these have a project already like rootstock for smart contracts on bitcoin or Lightning Network for side-chains.
Yes I saw after another poster mentioned rootstock and other projects being built. The only problem I see for bitcoin is that its wasting too much energy just to keep the network going
(I know lots of people will scream at me for saying this)