I think it's a risk. They are in the experimental stage of the edition. Last experiment was to see what a re-release with reorganized information would go like (MotM). I'm not sure how that will be seen, and hope that the AE goes better (at least my opinion of how MotM has gone thus far).
This is an experiment with new formats, and testing the waters with presentation and promotion (at least as I see it) of what could be a relatively unknown (to most who play D&D) setting. There have been other lesser know settings put out, so that's not as risky, but...as we can see from the graphs, putting this out COULD be risky in how well it's accepted.
Note, they are also putting out Dragonlance, so it could be that it is hoped to be the counterbalance to Spelljammer if Spelljammer falls flat. I LOVE Dragonlance, but I'm not sure it's going to be a stellar success either (I hope it is, but...I don't know).