Is this not a huge 51% threat, or am I missing something? (besides BFL)
It really isn't. ASICMINER plans on maintaining a percentage of the BTC network. Any equipment they produce that will put them above that percentage is getting auctioned off/sold. After spending all of this time/research in building a dedicated ASIC and running a farm, the last thing they'd want to do is render all of that effort & profit useless by shaking up the very currency they're invested in.