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In response to your question, it really depends on how long his current page has been active and how long it has been indexed by google. If there are links pointing to his current bio, it will stay active in the SERPs longer. Overtime the original page will not show in the SERP's but it will be replaced with the new page with his middle initial. It is always better to have more information than not. It is just like long tail keywords. If you type his full first middle and last name into search,  he will most likely rank for all three queries as long as his domain has relevant authority. I hope this helps!