It might be a stupid question but, I am currently using Arduino Uno with the 16MHz processor, what is maximum sampling rate of data available to me if I want to read data of a sensors such as accelerometer?
I have a page about I2C. The speed of I2C depends on a number of things, such as the I2C clock (which you can change) and also how many data bytes are in a "packet". There is a fixed overhead of the device address in each packet.
A broad rule-of-thumb would be around 4700 bytes per second for a single-byte payload at the default clock rate. You may also need to spend time asking for a reading. I haven't read the datasheet (which you didn't link).
The datasheet for the MPU6050 may give you more information about how fast it can respond.