What do u 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 regenboog 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 of a muziek note and Scootaloo's a racing flag. Of course there's no telling until they toon it, but they are probably going to involve fixing stuff, singing and racing.

I WAS GONNA ASK THIS XD. I agree with the ones u zei (StarWarsFan7)

Applebloom eith a paintbrush of an appel, apple blossom. Scootaloo, a scooter (duh!), and Sweetie Belle, a microphone of 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 of something scooter of speed related. Sweetie Belle should get something musical, like u said. I'm not sure about appel, 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. appel, apple blossom makes sense, yes, but who knows...

Applebloom's can be like an appel, apple blossom with a bow on it as she likes to decorate
Sweetie belle's can be a muziek note inside a hart-, hart as she likes to sing and is so very cute
Scootaloo's can be a vlinder wings and a thunderbolt perhaps as she is a big fan of regenboog dash and is as snel, swift as a butterfly!!! :) I hope u all like my answer !!! :)

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

appel, apple bloom something like an appel, apple and a wrench
Scootaloo a scooter
Sweetie klok, bell a bell