Say you have multiple devices/sensors connected to the Arduino through I2C. Wouldn't at some point the devices won't get enough voltage if you add too much? And how would you resolve that?
Do you understand what voltage is?
Hint: Voltage, Power, and Current are all different things.
If you bought breakout boards with sensors, those boards have many times pull-up resistors.
You don't want too many pull-up resistors.
If that happens, use 4k7 pull-up resistors and remove the pull-up resistors from the breakout boards.
About twenty I2C devices on the bus is no problem. In theory it can be many more. Too many long wires could be a problem.
All sensors should be powered, for example with 5V or 3.3V, independent of the I2C bus.