What do tu think the CMC's cutie marks will be?

I agree with your idea of Scootaloo's mark, but I imagine it as the wheel of a scooter (maybe with a lightning bolt on it, to symbolize her idolization of arco iris Dash). SweetieBelle's could be a bell, maybe three small ones (since I noticed multi-marks normally come in threes Ex. Applejack-three apples, Fluttershy-three butterflies, Rarity-three diamonds)

Applebloom's mark is going to be harder to interpret. Let me think it over.

Probably these...

Applebloom's may become a hammer, Sweetie Belle's a microphone o a música note and Scootaloo's a racing flag. Of course there's no telling until they mostrar it, but they are probably going to involve fixing stuff, canto and racing.

I WAS GONNA ASK THIS XD. I agree with the ones tu dicho (StarWarsFan7)

Applebloom eith a paintbrush o an manzana, apple blossom. Scootaloo, a scooter (duh!), and Sweetie Belle, a microphone o bell.

That's a hard one! I know that Scootaloo and Sweetie Belle have unique talents already; they just haven't figured that out. Scootaloo should get a scooter o something scooter o speed related. Sweetie Belle should get something musical, like tu said. I'm not sure about manzana, apple Bloom, though. It would make sense that she would follow in the hoofsteps of her family and get an apple-related cutie mark, but she hasn't really shown any particular talent, so we can wait and see. manzana, apple blossom makes sense, yes, but who knows...

Applebloom's can be like an manzana, apple blossom with a bow on it as she likes to decorate
Sweetie belle's can be a música note inside a corazón as she likes to sing and is so very cute
Scootaloo's can be a mariposa wings and a thunderbolt perhaps as she is a big fan of arco iris dash and is as rápido, swift as a butterfly!!! :) I hope tu all like my answer !!! :)

My thoughts are manzana, apple Bloom's CM being a golden painted manzana, apple for her talent of art, Sweetie Belle's CM being a note with a corazón for her musical talent, and Scootaloo's CM being a winged scooter wheel for her amor of scooter riding.

manzana, apple bloom something like an manzana, apple and a wrench
Scootaloo a scooter
Sweetie campana a bell