I'm waiting for 75–80% off. Do you guys think it'll happen? Seems that with most GoG sales, this title gets omitted. Is that because Interplay doesn't like it being on sale, or because it's a new addition to the GoG catalogue?

I don't think anything more than 50% off is going to happen for Interplay titles. The only time I have seen a better deal is when GOG had a special 'pay what you want' deal before Interplay jacked up the prices on all their games.