Official Nintendo Magazine will make a "world exclusive" Nintendo reveal in its 57th issue, released June 16.
The mag says: "Speaking of the future, you may want to mark Wednesday 16 June in your diary. We'll be revealing world exclusive details on a top secret new game in the next issue of ONM. We had to make sure we cover this new game which is why ONM 56 and 57 are both being released on a Wednesday rather than a Friday as usual."
For the record, June 16 is slap bang in the middle of E3 - so you know it's going to be good.