Hey all. I doubt that these observations are particularly original, but I thought that I would address them anyway.
First of all, I am of the opinion that what's happening with the flashsideways may be similar to what's happening on Fringe. What I mean by that is that these two separate realities may be on the verge of a collision or something involving an endgame in which only one reality survives. At the very least, these realities are probably going to start leaking into each other.
If you can live with that, let's examine three separate incidents in "The Package."
1. Sun gets aphasia. Yes, aphasia exists and this kind of thing CAN happen... but it was kind of lame. The question is, are we being told to accept the ridiculous plot device and to move on (via Miles and Frank's brief exchange), or are we being set up for parallel world stuff? Sun can't speak English in the flashsideways world. Now Sun can't speak English in the MTL. Sure she can still read and write English (which is consistent with some forms of aphasia), but who's to say that everything leaked through?
If we watch the scene where Locke chases her again, she falls unconscious in the MTL and then opens her eyes in the ATL. I don't think that was a coincidence.
2. We see Kate looking REALLY weird as she stares blankly at nothing. Sawyer comes by later and says something like "You looked like you were in another world." Maybe she was actually in another world! At least maybe her consciousness was.
3. Widmore tells Jin that, should MIB escape, everyone he cares about will "cease to exist." Not be destroyed. Not die. Cease to exist! Sure, he could simply mean die, but the lost writers are very good at what they do with their dialogue. Maybe Widmore knows about the alternate reality and, should MIB escape, he won't just kill everyone on Earth, but rather, he will cause this reality to cease its existence.