Can you see a time when all Jews will follow the same customs? For example, Sephardic Jews eat kitnyot on Passover, while I, as an Ashkenazic Jew, am not allowed to eat some kosher legumes and plain white rice on Passover. I believe that if some Jews say it is okay, there should be no problem with it for all Jews!
Once upon a time, in the isle of Ireland, many people thought it a good idea for everyone on the island to grow the same sort of potato. That way, everyone could use the same farming techniques, everyone would plant and harvest at the same time and all potatoes would taste the same.
The result? One little bug came along, and within a week or so wiped out the entire crop of Irish potatoes. To this date, Ireland has never returned to its population size before that.
The Jewish People has managed to survive every sort of physical, social and spiritual blight, plague and persecution in the book for three and a half thousand years. Perhaps, just maybe, diversity of custom might be a factor in their survival strategy.
Of course, the Torah sets limits. Just as the rules of harmony set limits on what makes harmonious music and the rules of color and symmetry set limits on what makes an attractive design, so too Jewish law provides us the parameters to determine what is kosher and what is not, what is healthy for the soul and what is detrimental, what it is that G‑d wants to see in His world and what He wants booted out. But within those guidelines, don't you think He might enjoy a little variety? Or just Irish potatoes all day long?
So each of us keeps the customs of our family and our community. They are very special, even sacrosanct to us. And at the same time, we appreciate and respect the customs of every other Jewish community and family. It just makes G‑d's dinner plate that much more colorful.