The image below shows a typical I2C transmission. A closer look to the signals discloses small spikes in the signals. These are consequences arising out of cross channel capacitances Cc.

In general, crosstalk should not be a problem as long as the resulting spikes are not too large. Cc itself can be minimized by using as short interconnections as possible. Increasing the serial resistors Rs and termination Rp can help to reduce the effects of the cross channel capacitances Cc.