Considering Hollow Knight's recent peaks after Silksong's trailer is 50k-ish (and will likely grow slightly higher over the next week), I'd probably say around 100k-150k.
>>719200873
>>719201119
Theres a lot of hype surrounding Silksong, especially for an indie game. But I'm not convinced it'll reach 500k+.
I'm aware that it is number 1 wishlisted on Steam, but its worth remembering that it's been wishlist-able for 6 years, and its very common for people to wishlist games they'll never get around to buying.