I don't think I totally understand what you mean here. Are you saying that you want a Outlook app update or do you mean what's the outlook for an update of the Lumia 1320? If you mean the latter, it's not happening. I would suggest another phone if you wish to stay in the Microsoft ecosystem.
If you can find a used Lumia 950XL, that would be your best bet. Alternatively, I'm not sure of your location, but you can also try to find the HP Elite x3 or the Alcatel Idol 4 Pro (or Idol 4S if you're in the United States).