The main point of presales is keeping interest in the game. If a company had a tendency of reducing the price of a product before general availability, some people would wait. They would then lose sales to those who lost interest while waiting. By offering the presale early and at the cheapest price to be found, they make sales to people who are currently convinced they'll buy later. Some of those people wouldn't buy later if they waited. By this logic, if anything, I'd expect them to raise the price (although I'd expect that to be currently communicated with the current price being a "discount", and it's not, so it probably won't go up)