As long as ES are held in check, true classics will be classics and retain a healthy value or more.
1. Hulk PF 1 is a small ES for its popularity of the character, a fantastic sculpt (whether you "like" it or not, the sculpt, attention to detail, paint finish, and representation of Kirby sculpt were all well executed by SS). A new PF Hulk (Hulk PF 2) done by SS will be a different rendition of the Hulk. If Hulk PF 2 is sculpted well, it will serve as a "companion" piece to Hulk PF 1, and hence maintain or increase value of Hulk PF 1. If Hulk PF 2 is not a great sculpt , then the obvious happens in value and demand to Hulk PF 1. And in fact, if Hulk PF 2 is executed well by SS, the saying wiill be "get both they are great on display together."
2. SS IM has way to high an ES AND to many choices, even for it's character popularity. As been mentioned twice, this why it is not holding it's high value. But having said that, the IM maq exc is STILL holding it's value way above the release price from SS, and in an economy that is not recovered yet.
3. Because of the superb job by SS on Venom Bust 1, it's low ES, and it's classical rendition of it, this sculpt will maintain a value way above it's release price. It falls under point 1, the example of Hulk PF in this post.