Impossible to say for sure. But my guess is that, in general, if demand increased substantially due to a massive (and unlikely) spike in prices, then, yeah, more high grade copies of these books could possibly emerge from personal collections.
But which DC 100-pager, exactly, will EVER approach Hulk 181 in terms of overall collector demand? The only one that comes close is probably this one...
DC SS #5
...a book which, while obviously in shorter supply (in all grades) than Hulk 181, also has a much more limited overall appeal than the first appearance of Wolverine. And I really don't think that's likely to change. Do you?