Remember that BOGO only applies to heroes bought through the in-game score for Gs, not those bought online or through Steam. Also buy your heroes one at a time and open each box before buying the next - you might open someone you planned to pay for.
Patch notes are out for the new version, and the changes are colossal. Characters will be getting extra skill points (30, IIIRC), the skill level cap is now 50 (up from 40), some characters are getting new skills (Deadpool gets a mnigun), the Omega System will be entering public beta (you will keep all points earned after the wipe) and there's been a mass consolidation of power buffs to provide one of six fixed buffs at a cost to maximum Spirit that decreases with each point in the skill. The rework is so extensive that all characters will receive a free respec.
One warning: you will get fewer skill points at lower levels and more at higher levels. This will make it very hard to level Doctor Strange without using a Retcon once he hits 45, so if you've had him parked get him up to at least 30 now if you can.
Oh, and everyone is getting a free STASH tab as part of the 365-item giveaway.