Most anime shows (at this point in history) that get 10-20% are for children or at best family-oriented, which gives them mainstream appeal but they're usually not the kind of thing most of us would appreciate.
It may continue to be a disappointment for the broadcasters if ratings don't improve...but the worst consequence I can imagine is a change in time slot either one third or halfway through the show, and maybe some animation budget cuts that could be corrected for the DVD release anyways.
Sunrise (and whoever shares those profits) can't possibly want to throw away the kind of DVD and related materials sales season one had, despite its poor ratings because the original show wasn't exactly a TV hit either, so I'm fairly confident the show will live to see its end, one way or another. Even if it fails to get mass appeal, otaku appeal will still bring in money. Not to mention that canceling everything so abruptly will just maximize the losses for everyone involved, while a gentler landing will at least reduce them, if not outright cancel them.
I also hope that the plot doesn't suffer, in any case, whether the schedule changes or remains just as it is.