(They can't decide what to call them, so I'm calling them Rocks for now.)
For my money, there are two things about the Rocks that Marvel is going to have to handle carefully:
1) Having every damned movie revolve around one or another of the frelling things.
I mean, you could. You could make Ant-Man's MacGuffin be the Space Rock, offering its effects as the source of his shrinkage (rather than being wet and cold). Quicksilver's and Scarlet Witch's powers could be tied to the Time Rock and Reality Rock respectively (a twofer!). The entire plot of Doctor Strange could revolve around the Soul Rock; the gauntlet itself might have to be made of Vibranium because MacGreasons, giving us Black Panther.
The problem I'd have with this is, I'm already tired of All the Plots revolving around Rocks. Sometimes it makes sense (Guardians), but the universe is bigger than the Rocks, and I'd really prefer the movies to reflect that.
Also that would lead to the second thing that would bug me...
2) All (or majority) of Rocks being located or directly tied in with Earth.
Guardians dodged that bullet (barely), but Thor: Dark World was grazed. Captain America 1 and of course Avengers went straight to the ER, riddled with GSWs.
I'm not sure how they could get around this, because of course the MU is kind of Earth-centric. But I feel like having all or most of the Rocks accessible on Earth would require some fancy footwork to not be too handwavy (please forgive the mixed metaphor).