But what will make it achieve $ 5 and when will it happen?
It will reach $5 caused by the adoption. These days the adoption rate for the ADA smartcontract was not so high compared with another blockchain like BSC. The daily transaction is still less compared with the BSC.None knows about when ADA will reach $5 and only the time will tell us.
Will Cardano position itself to replace Ethereum and tackle the issue of huge gas fees? 
I will not. There's no reason for ADA to replace ethereum. i do believe that if these platforms will be co-exist instead of replacing one and each other. The competition was very strict but there's no way for new platform to destroy the old one. So many old stories about this happened in the past but the result will always be the same if ethereum will become the big crypto .