Is there going to be a new wallet after 300 blocks???
Not at all, if you have still updated your wallet to the last version 1.6.1 you have nothing to worry about.
If you haven't do it yet well... do it
I guess the question is how will one use stealth address if it's not yet implemented.
that`s also not 100% clear for me, is the stealth address now working as soon as i create a new address?
This feature is implemented for all wallets >= v.1.6.0.
It's just disabled on the mainnet until block 460 000.
Stealth addresses look a bit different, they are longer than the usual ones. This is a screenshot from the testnet where the stealth addresses are already activated.