1. These new Central Bank coins are they going to be stable coins or not?
2. What will happen if they are not stable coins? If holding them will be profitable many will leave crypto space and focus on these new coins?
3. Maybe people will just use them as a plus since it's from the government?
They will be stable coins that's backed by each central banks national currency. From what I know so far, they won't be traded on exchanges. They will have a spefic use case and will not be subject for speculations unlike crypto coins with open blockchains (btc, eth, ltc, etc.) so do not expect to profit from them.
4. Will regulations still come after this?
Obviously, no. Central banks will have government approval before proceeding with these coins.