I was watching some clips of season 4 and I had gotten to the clip where Regina and Henry are discussing how when they find the Author, they will ask him to write Regina a happy ending because that is what she wants.
Now if we go off some of the spoilers and theories, then maybe Regina will succeed in altering her future and possibly her past. If that happens then what we could be looking at is Regina realising that getting what she wants doesn’t get her what she wants. It could mean that Henry would have been either erased from existence or not being given up by Emma.
It is basically another reversal of the whole if Regina hadn’t become the Evil Queen thing and it also ties what Robin Hood said at the end of season 3 of it all being about timing. To quote that man ‘Maybe everything works out when it’s supposed to’. It will still be a good episode if it does happen. I like alternate reality episodes.