Do not take this as official confirmation of anything, but there's a pattern that Arrow has always stuck to with their premiere dates. Arrow always premieres right around New York Comic-Con. Whether that's by coincidence or design is another story, but it's happened three times in a row.
So with that in mind, and assuming the CW doesn't move the show to another night, I predict that the Arrow season 4 premiere will be on Wednesday, October 7th, 2015. I will update this if I hear anything different.
I have good reason for predicting this. Check it out:
Arrow season 1 premiered on Wednesday October 10th, 2012...the night before NYCC.
Arrow season 2 premiered on Wednesday October 9th, 2013...the night before NYCC.
Arrow season 3 premiered on Wednesday October 8th, 2014...the night before NYCC.
If anything changes, I'll let you know. But for now, expect Arrow season 4 episode 1 to arrive on Wednesday, October 7th.
But the big question, of course, is always who the next big baddie is. Well, now we know...
Arrow Season 4 Trailer
Alright, so it's not quite a trailer, but ust for kicks, enjoy this video of Marc Guggenheim tormenting teasing fans about what's in store for Arrow season 4...