I think it probably is possible to practice 10 hours a day, i know as a beginner (as i am now) i was practicing 4 to 5 hours a day, you know that saying " time fly's when you are having fun" it was only when my finger got sore and finally blistered that i cut back. (no blisters now but still sore and healing)
i think all this depends on your drive, some people just fancy being able to play the guitar so they dabble a bit, but some people have a yearning or such a strong drive that they just wont put the thing down and are constantly looking for things to play or improve.
Depending on why you are playing,trying to learn, will probably determine where you will end up and how good you will be.