Improbable because these credits come from the merchants, not from American Express. Merchant-specific benefits are always temporary, and to my knowledge American Express has never reduced the annual fee on any card, BUT they may offer larger retention bonuses in the aftermath if they can see that you actually used the benefit.
Any guesses on what the arrangement is between Amex and Dell with this $200x2 credit on the Business Plat? I would assume that Dell is getting something from Amex, other than the hope that the Amex Biz Plat holder will spend big enough to offset the $200x2 reduction in the prices.
BTW, I recently bought a webcam/speakerphone for $352. I've been something close to worst-case for them with this benefit. Usually I'm barely above $200.