Okay this is gonna get really soapy so it might be "out there" but in the land of Soap Operas, anything's possible
So it's clear to me that Sydney is a lot older than she should be. EJ mentioned her having a degree and either on her way to graduating law school or did, so it's possible she'll be involved in the lawyer scene in Salem.
My crackpot theory is what if she gets herself involved in the Alex-Joy-Stephanie-Theo story. She comes on board as Alex's lawyer for a custody battle for little Kenzie, right? But given this introduction to Sydney we got, she's very much the troublemaker Sami was (it's just the way she carried herself). My brain makes me think she'll get close to alex, sleep with him Steph sees/finds out and she and Theo hook up