I wouldn't want to start off with a new employer by negotiating for a bonus buyout and then staying long enough to get my original bonus (and expecting the buyout anyway). I would be interested to know if anyone has done this successfully. If I thought I had the upper hand in negotiations, I'd just ask for more pay, or a signing bonus independent of my foregone bonus.
So, yeah, I definitely have never solicited a bonus buyout and then done a bait-and-switch. But I've never actually solicited a bonus buyout -- I negotiate in terms of compensation I receive, not labels on it. I've had companies offer me bonus buyouts before, sometimes quite significant, and I've always taken that as a direct indication of their assessment of my value, not as something specific to the time of year.
Of course, the new company can say "you get X signing bonus if you join this calendar year, and x/2 signing bonus if you join next calendar year, since time is of the essence".