Communication is an interesting thing. No matter how many years you have been talking, writing or even managing other people, your communication abilities fluctuate.
While it is mostly true that those with concise and clear communication skills are more likely to be promoted to leadership positions, the skills that got you there won't keep you there.
Communication skills are one of those things you have got to be consciously improving on a regular basis. After all, we can get so lazy in our communication. Have you ever tried to write a directive email while talking on the phone, before rushing to a meeting? The chances are your email was unclear and confusing.