when will segwit activated? 
Q1 2018 but that can mean end of this month or march afaik.
And at that time we will need new wallet for staking?
When we are out of testnet and push the updated client to the public repo we will provide a link for download.Until then staking will carry on as normal in the current client.Nothing is affected until we pass the stage where old clients no longer stake but the new client will be ready by then.