Hot wallet and cold wallet If you have a online site that accepts bitcoin deposits and users can withdraw their balance, Is  it possible to have the deposits go to the watch-only address of a cold storage and the withdraws come from the hot wallet?

If yes, then basically I'll have to give a programmer my private key for the hot wallet and just the master public key for the watch only-address on the server. Am I correct?
The Answer is No, you can not do this. Reasons are below.

It seems you may be confused.

The point of a cold wallet it to store the coins offline, adding a watch-only address to a cold wallet does nothing, other then letting you see that address.

(I could add your address as a watch-only and see your balance as well, but that doesn't give me access to your coins)

If the coins are in the cold wallet then you have to send them from there, generally by creating and signing an offline transaction.

If they are in the hot wallet (even if being watched by the cold wallet) they you can send them from the hot wallet.