Personally, I think Nokia won't release a Pie Beta for the Nokia 8 Sirocco. Since as we all know the number of Sirocco users are pretty low compared to Nokia 8 or other Nokia phones. So, even if the beta is released there is no certainty that most of the Sirocco users will participate in the beta labs. However, Nokia might release the Pie update for 8 and 8 Sirocco nearly at the same time like they did with their Nokia 6.1 and Nokia 6.1 Plus.
Answers
However, I might be wrong.