Some of the Playtesters keep mentioning that more was coming, and even with the recent release of 9e, we don't yet have the "full picture." I just assumed they were alluding to big changes in upcoming codexes (and perhaps they are), but now it also seems that some of the big changes are related to weapon profiles and abilities, and wargear. We've already seen the probable change to Storm Shields, with the Bladeguard's rules for those, but now with these leaks, we're beginning to see a whole lot of major changes to some of the Marine weapons. Check out the OP in New and Rumors here.
But, here is a bit of a summary:
Onslaught Gatling Cannon is now Heavy 8
Twin Accelerator Auto Cannon is Heavy 6
Multi-Meltas are now Heavy 2, and their ability has changed to D6+2 damage when shooting at a target within half range.
Heavy Bolter on the Invictor Warsuit changed to 1 shot at S5/AP-1/2D (less shots, but 2 Damage)
Ironhail Heavy Stubber now Heavy 4 (probably), which is a gain of 1 shot
Incendium Cannon gains a point of Strength to S6.
Just based on these changes alone, it looks like one of the major efforts for 9e play testing has been doing a thorough pass through all of the weapon profiles to ensure lesser used equipment is made relevant.
If true, that's definitely big news, and will have a major impact on our lists.