So what happens after block 300k? I have not stakes my coins yet, but was planning on doing so this week. Is it better I wait for the new wallet?
Block 300K will be the last mined block. After that, it will be only Proof of Stake. This will help to increase the worth of the coin. You are welcome to stake now as once you have the new wallet, you will just need to switch to that. Always keep a backup of your wallet.dat file.