It would have been great if they had included the Avengers World issues into the 2nd Omnibus. Otherwise I just don't see them oversizing Avengers World. I have both the Time Runs Out and Secret Wars OHCs and feel pretty miffed about purchasing the former as I will end up picking up the 2nd Omnibus and double dipping as a consequence.
This is how Krisis "ideally" mapped out the 2nd Omnibus on his website:
Avengers by Johnathan Hickman, Vol. 2 – Collects Collects Avengers #24-34 & 34.1-2, New Avengers #13-23, and Avengers World #1-21.
It would be very cool if Marvel changed their minds and decided to do that but I'm not holding my breath.
Marvel are mainly in it to make money and if a run is popular, they will repackage it in various formats which of course can be annoying when we end up double dipping.
@Yaggi_Rick, event OHCS usually go on clearance (Secret Invasion, Siege, AoU, Infinity can still be found at bargain prices) before they consequently go OOP. I would be on the lookout for one at a good price and pick it up.