If you do this, I would expect that the retention bonus would be rescinded and be pleasantly surprised if its not. Amex's systems seem to have gotten "better" at noticing these things automatically, I mean seen plenty of posts from people who had 40k MR disappear when downgrading an Everyday Preferred too soon after taking an upgrade offer.

My AF hit a few days ago. I got a 50k retention offer last year, I may see what if anything Amex has. If nothing I may just close the card and go home. I have the CS Plat which I got a few months ago, and with those new terms MS has added, seems that there is a real risk to them trying to weasel out of paying the engagement bonus in a few months.