Yes, that could happen. In fact however, one reason (of many) that horror collectors started flocking to BA books was because the pre-code market became too expensive for many. So, you end up with a possible yo-yo effect. If BA starts getting too steep, they might come here if the market has become more favorable to their purchasing power. OR... they might move on to Copper Age horror, which really could be the next hot area in horror.
In general though, horror goes in cycles. Right now the pre-code is soft and the BA is hot. If the BA cools off, there's really no guarantee ANY horror age will heat up in it's place.