Sadly, nothing bad will happen to reddit no matter how many people try to protest with pixel art on /r/place. Last year, admins unabashedly removed entire swathes of canvas that they deemed inappropriate, sometimes catching legitimate art in the crossfire. Not to mention the admin who got caught red handed placing multiple pixels off of the timer, with video evidence.

So no, a giant fuck /u/spez will never be allowed to exist long enough to be anywhere close to complete. They'll do the same thing to any API related banner or whatever you might think of.

The best thing you can do is not engage. They are doing this again so soon after the last one because they desperately need clicks and traffic to boost their site metrics for the upcoming IPO.

Besides, it's just going to be a canvas covered 75% in flags maintained by bots anyway because reddit sucks at programming in safeguards to prevent abuse, so your 1 pixel of contribution won't mean squat.