Not necessarily. For example, I've had optic neuritis myself. I don't happen to have had any spinal lesions, but the two aren't mutually exclusive. I could have a spinal lesion next MRI or never. In MS, there aren't really any certainties or guarantees. An episode of ON doesn't mean the spine is 'off limits' for the rest of your life. In MS, other episodes will occur, and their evidence will be located anywhere in the central nervous system.
I notice this is your first post. Have you been diagnosed with optic neuritis yourself? Welcome to the forum.
The short answer is NO, because if a person does have MS the demyelingating lesions can develop in the brain and or the spine, regardless of if they have or had Optic Neuritis or not.