GBTC has been an accurate price predictor of Bitcoin only because of two unrelated factors:

1. That GBTC is monstrously overpriced.
2. That Bitcoin is monstrously growing.

While I agree that Bitcoin will go to $10000 eventually, I cannot endorse GBTC as a predictor, as the correlation between these two factors is weak, at best, and hardly suitable for any kind of predictive algorithm.