The tweets showcase a change to shortcut loadouts, which will increase the threshold of the mechanic to eight slots in all. We'll also be getting a long-awaited "lock" mechanic, which will let you sidestep accidentally selling or crafting armor pieces you don't want to get rid of. This has been a thing for many years in many high-profile games with inventory management, and it's very much welcome with Rise.
Note that this is all coming in the next major Monster Hunter Rise: Sunbreak update. Title Update 2 will arrive in "late September," and we'll likely get full confirmation soon, including a stream to show it off. Capcom has been running a thankfully predictable and effective hype campaign for these updates.