This a a quick update:
Sergey Sirorkin has just been confirmed to be teamates with Lance Stroll at Williams Racing for 2018. Sirotkin beat Robert Kubica for the seat. This decision confirms that Pascal Wehrlien will not be driving in F1 for 2018.
Photo from F1.com
Robert Kubica has also just confirmed that he will be Williams’ develop driver for 2018.