There's a reddit rumor including:
- PC version is Battle.net
- PvP is four player
- Basic PvE teams are four player, wasn't sure on raid count
- Same three classes, but totally redone sub-classes
- You have two primaries now, one regular damage, one Elemental
- The base locations are theee Jupiter moons and Earth, but they're much bigger zones than the first game
- Game has way more content than Destiny 1 both before and after level 20
- Heavy machine guns removed in favor of grenade launchers
- New weapon type they didn't want to spoil
- Your sparrow unlocks after you beat the game
- Looking for group tools of some kind for end game, didn't specify what
- I believe they thought it was 30 FPS but wasn't positive
- The social spaces are divided into 2 (or 3?) one at the start of the game, the other opens up at the end. Open areas were named as Earth, Myraid, Titan and Ganimede
- I can't remember if there was anything else, someone here probably remembers