My bet is that the lower-end mini is being discontinued completely, much like the lower-end Apple TV. Maybe the higher-end one stays the same but just gets a price drop. Why else discontinue the lower one but not the higher-end one?
As others have suggested, perhaps the high-end model is becoming the new low-end model, and maybe they'll introduce a new high-end model.
Or just have one mini.
Or do something crazy and unexpected, because with Apple, you never know until it's out the door (or they issue a cease-and-desist