I doubt that Amazon would raise the price on those who already ordered. From my experiences with them, it's just not how they do business. For example, the Retron 5 dropped down to $76 for people who preordered it a while back, and despite the error, Amazon did not readjust the orders back to $100.
The HD collection disc is not quite the same as the one in the legacy collection (despite it having the same name in the xmb). The legacy disc has MGS1 and MGS2 digital comics under the xmb video section, whereas the hd collection does not.
Good thing I had an honest buyer who already left me positive feedback.
Bought two copies at a local FM, left the remaining one for someone else. Opened one to play MGS2, and sold the second to make the first "free". Seems reasonable to me.
I wouldn't be surprised if it outsells all current PS4/XB1 games. That's not really saying much though, given the overall lack of quality games on both systems.