To be fair, you probably couldn't publish your game anyway, since the rules are copyrighted. You'd have to rework it considerably in order to make it sufficiently different as to be legal.
I do agree, though; having all rights to non-winning entries convey to Days of Wonder is a little shaky ethically. A better solution would be an indemnification clause: If you submit your work, you agree not to sue if Days of Wonder later produces a similar game. That would protect both parties. It isn't in the interest of the lawyers to protect anybody who hasn't paid them, though.

It is also worth considering that just because a company conducts itself ethically now, that does not necessarily mean that it will continue to do so in the future. Or that Hasbro won't assimilate it.