When I think about the amount of time it took for credit/debit cards to catch on and be used in most places, or the amount of time it took before online shopping become a normal thing that most people do. 5-15 years seems pretty reasonable imo for a timeframe for bitcoin to start to reach it's full potential.
How long did it take for credit/debit cards to catch on? Remember, new technology moves faster and gets implemented quicker now than it did back in the day, so I think if Bitcoin will ever become mainstream it will do so well before five years. I could easily see 2-3 years.