That's the release date of Infinity #3.
Now, Infinity #2 has a pretty big spoiler which we haven't touched on. But since Marvel is asking the question, that's what we'll do now.
In today's issue, it's revealed that the secret the Inhumans are hiding, beyond the usual Infinity Gems, is that one of the young Inhumans is the son of Thanos.
And clearly that's a thing. Whoever he is…