Well they are certainly fleshing out he wood elf faction.
Not really. Sylvaneth are their own faction now, the Wanderers are the other faction that got split from the old stuff.
And the two factions aren't on friendly terms. The Wanderers fled to Azyr before Sigmar closed the realm off during the Age of Chaos. Alarielle hasn't forgiven them for abandoning her and Ghyran to suffer at the forces of Nurgle. She went into hiding, but the Stormcasts found her, but in inadvertently led Nurgle in as well. They fought Nurgle together, and she has now decided to join the war, scattering the realm of life with acorns to grow an army.
The Wanderers may have returned to Ghyran now the Realmgates are open again, but they're not necessarily welcome.