I note that IDW is listing the Teenage Mutant Ninja Turtles: Prelude To Dimension X title that was free for Free Comic Book Day at the beginning of May, on the Kindle for the 31st May (here in the UK). Free, naturally.
As a prominent title for Free Comic Book Day, it may indicate that a number of other publishers will be making their titles available for free, digitally, as well, around the same date – it has done in the past.
Not all by any means. But… some.
Worth checking back in a couple of weeks?