You can use more sensors on 1-wire. It is a bus and each DS18B20 has unique address.
If you need other sensors on I2C then you can use both I2C and 1-Wire. Arduino has specific pins for I2C and for 1W any digital.
And also, there exists converter I2C/1-Wire like DS2482. Adrduino will communicate only on I2C in such case.
I know, but it's a shield. It doesn't use all pins of an Arduino. Just check which pins it uses and don't use that for the 1-wire :)
Thank you, guys. I understood, but I want to use I2C protocol. Do you recommend DS2482-800 bridgefor it, or it has another way in the code to set DS18B20 into I2C? There is my question.