I came out to some of my family and my significant other before I went to therapy, but I felt pretty sure they would have positive reactions. There were some family members that I put off coming out to for a looong time, because I expected a negative reaction (which I was right about).
If you feel like the people you come out to will be supportive, then don't wait until therapy. If you feel like they won't be, then wait. It's important to have all the support you can get in your corner (be it therapists or family memembers) before enduring negative reactions.