I do think enough people believing this could happen, and thus hoarding pennies, could increase its likelihood.

It'd grow a popular constituency for the rebasing, and create a change shortage that's most-easily addressed by incentivizing the release of instantly-more-valuable penny hoards.

Fill your jars, then pass the idea on!

(Does anyone know someone high up in this '4chan' memetic-prankster cooperative I keep hearing about? Nah, they'd probably just trick Congress into doing something useless like rebasing the penny to 4¢.)