I like how Pepsi announced that if you manage to pre order a bottle tomorrow, they won't be sent out until after xmas. They can't get this promotion right.... it's almost laughable at this point.
I think a LOT of people underestimated the popularity of Back to the Future in general. While not an obscure franchise by any stretch, I'd argue that it doesn't typically garner the same sort of mainstream attention that Star Wars, Star Trek, Harry Potter or the Lord of the Rings films do. That may seem like an odd conceit to us, but perhaps not to those outside of fan culture.
Companies like Pepsi and Nike (who only made 500 pairs of replica Bruins) didn't foresee just how popular these replicas would be, so they made a limited number to be safe. In underestimating the popularity of the franchise, they also underestimated the demand for their product. That said, it doesn't help that Pepsi and/or Amazon botched the release either. Now Pepsi is scrambling to put these back into production in order to save face, but manufacturing 13,000 at the outset probably would have seemed like a risky venture on paper to them at the time. This isn't a company that makes movie props. This is a company that sells soda. They were a bit out of their league here.
I do think the preorder route is a safer bet than the original sale was. Madrid skateboards did this for the 30th anniversary Valterra decks, taking orders for two months and then making enough boards to fulfill them. Mattel also did that with the replica Hoverboards, making enough to fill a preorder quota and a few extras as well. These companies had orders in hand, and knew exactly how many to produce without producing surpluses or shortfalls.
It'll be interesting to see what happens tomorrow. If the second batch sells out as quickly as the first, will there be a third release? A limited release? Would these just become mainstream? If Pepsi's making a substantial amount of money on these, and the trouble of producing them isn't bothersome to them, I would think they'd keep making more That said, they could also just decide to wash their hands of the whole mess and say "That's enough. We're going back to making regular soda now."
Hindsight and conjecture, ladies and gentlemen.