It depends on several factors...
1) how well it is cared for, e.g. sunlight, water, feed, pest control, etc.
2) whether it is currently planted and settled in soil or needing to be transplanted (sounds like its planted)
3) whether it is a seeded tree or grafted tree.
Generally, it would be another 2-4 years if it is a grafted tree and currently well settled and well taken care of and the better it is managed the shorter that time frame.
With top of the chart care, you might even see some blooms next spring.
If it was 1.5-inch diameter last year, what is it now? If growing good might well be less than those 2-4 years estimate.