I told my boss in 2009 that we needed to start considering a succession plan. I was a regional CEO with a major global megacorp. My initial proposal was to stay 3 more years, giving me 10 years total in that role. He insisted on 4 more years and offered a package in return. I found a replacement and trained him, but 3 years in, he went wonky on me. I approached my new boss and told him we had an issue with my intended replacement, and that we needed to try a new approach, but I had less than 6 months on my contract and offered to extend if he wanted me to. He had a different strategy in mind, and brought someone from outside to take my region role, and to leave my would be successor in Japan (I was a dual hatter, Japan and Asia) in place for a while longer. So we agreed I’d depart as we had scheduled but I could not announce it to anyone except my family, because I was a “named executive”. My local announcement had to coincide or follow the announcement to the markets.
So it really depends on the role you have in the company, how many and how badly the eggs will crack if word gets out too early, and even if there are legal ramifications if word gets out before official announcements are made, as was my case. Could even be an issue if the company owner is in talks to sell, with you as a key employee, but you not being aware of those negotiations. If it gets out the wrong way at the wrong time, it could kill the sale. Really, only you know the parameters on this one. Good luck.