Elizibeath revived her dead son with magic. That is a big deal, which must carry a big price. Sasha has already dished that Sean will have side effects from being resurrected. Does it mean since he lived someone close to him must die. We know a number of family members are coming from Vienna.
You will have an unstable Juliette as a hexenbiest looking the take revenge on Adalind. You will have Sean dealing with the consequence of his resurrection. You will have Nick dealing with Juliettes, Sean, and the Royals. He will be busy.
This means you have the gang in a weakened state and the Royals at there best. This will be a real slap in the face when they still lose.
The gang does have one thing going for them, the element of surprise. Especially with Vikor and Adalind they are expecting to show up in Portland that is Grimmless.
I admit I kind of feel sorry for Adalind. When she sees Nick has his Grimm back and Sean is alive and well she will be shocked, but when she sees Juliette as a hexenbiest, she just might lose it. Of all of the characters Adalind is the one character that has no friends or alies. We know Clair is expecting in RL. Once see finds out about Sean, Nick , and Juliette it will make for a good reason for her to leave for awhile.
It might be Adalind help Sean with his resurrection issue in exchange he helps her get out of town and away from Viktor. I don't see how she will make a return to the show.
The actress is really good... there needs to be a way around, making her "join" in with the group, as she's always that "untrustworthy" stranger... only fighting along side them, but you can smell the tense when she's around. like they do accept here, but there's always this tiny bit of "I got my eye on you...".
This way she will stop being a "villain" and still will be on the show.
I will use a charmed reference this time. I see Adalind becoming like cole. Who went from trying to kill the charmed ones to working with them even thought he was never really excepted. The same was true with Spike in the Buffy series. We can'tsay that about Sean becuase he was not a vilian he was ony after the key. For Adalind to change sides she would be the redemption character. From what I have seen all of these types of shows have a redemption character.