How many devices can be daisy chained via SPI/I2C?
The devices are not "daisy chained" in an I2C setup.  

The total number of devices depends on the capacitive load on the bus.  Each device, and it's associated traces, add capacitive load.  Look at your devices datasheets for how much load each device will tolerate.  You'll have to do some math and know something about your PCB layout if you really wanna make sure your design is OK.