There is nothing to worry just yet.
The casper protocol won't effect any smart contract much, it is just a new consensus protocol. I think the only thing that will effect is that they will use RANDAO which is a truly random function for blockchain.
For eWASM it is still in research state there isn't a complete product anywhere yet so ALL HAIL vyper and solidity
Sharding will effect in ethereum in many ways. The smart contract will have to upgrade to adopt it because user will change from one chain to another chain. This is a
problem that is still in research, because you will have to think about backward compatibility.
So in short eth 2.0 is still young. You can think it is like Brexit, they said many times that they will leave EU but i doubt they will