The blockchain only shows addresses, not wallets.
By seeing one address in a wallet, nobody can ever guess any other address.
Having multiple addresses is awesome, because you can isolate transactions from each other and by using a "mixer" you can send BTC from one address to another without anyone else even knowing you own both adddresses.
Generally, a wallet will send from multiple addresses in the wallet when it needs to (e.g. one address doesn't have enough to fund the transaction). That transaction will tie the addresses together.