The following message, about Xbox One pre-load size, was released today on the official Gears of War 4 Twitter:
"Good news! #GearsofWar4 pre-load for XB1 digital pre-orders begins later today at 5pm PDT (12am UTC). Expected download size will be 54.6GB."
Later on, the developers added some info for PC players:
"#GearsofWar4 PC pre-loading is coming soon and will be well ahead of launch! We will be sharing updates on that in the near future."