Some stuff about MGO3 got confirmed.
Metal Gear Online will support up to 16 players on PS4, PC, and Xbox One, and up to 12 players on PS3 and Xbox 360.
Maps will be fairly large
There will be bullet drop but it will differ from the single player mode such that it will make MGO more balanced
Sources: MGSV Japanese site http://www.konami.jp/mgs5/tpp/jp/products/index.php5 for the player size
MGO twitter for map size and bullet drop. The MGO twitter account answered some fan questions regarding MGO too.
Anyone want to talk about MGO1 and MGO2 can do that here too