@Zerowinger

So, do we take this to mean Opaline will make use of Starlight’s old spell?

It is not the same; Starlight could only take the cutie marks which she needs to store in a special cabinet with magical properties, Opaline on the other hand can store the cutie marks in her own magic. So if the Mane 5 want the cutie marks back, they have to defeat her without magic or get help. And Misty will then have a very important role during the first showdown between Sunny and Opaline. As predicted, Sunny will lose the first clash. But she will return with her friends - Misty included - as soon as they figure out how to get their cutie marks back and make themselves immune to her.

We now have a good idea of ​​how Opaline could steal magic; her alicorn properties allow her to store huge amounts of magic, and the spell of Starlight makes it possible, because the cutie marks are magical. It won’t be a stretch for her to go from cutie marks to dragon fire and ordinary magic. This makes Opaline very formidable in battle, and since Twilight defeated her, it must have been an epic battle where the Mane 6 (IDW) may have been involved. Now we know why Discord couldn’t stop Opaline, and why Twilight took Opaline’s magic, she had become a magical parasite.

This is a comparison to Kung Fu Panda’s villain, General Kai who threatened all martial artists worldwide after learning how to steal and assimilate chi. When Po defeated Kai during an epic battle, it was by infusing him with more chi than the general could handle. This will not be possible with an alicorn, but an important lesson from G4 is - that even the smallest and most harmless spell can do enormous damage to an alicorn not on her guard. Her strength will become her weakness.

So, do we take this to mean Opaline will make use of Starlight’s old spell?