to me, these are the reasonable assumptions,
the plane went down in the ocean, everybody that was on-board is dead
finding a wreckage site is increasingly not likely
there are countless debris in the oceans, whole containers fall off of large transport ships all the time, not to mention crap that is just dumped out there when no one is looking, reports of sightings will yield nothing conclusive
however, many months from now on distant shores, pieces of drivers licenses, passports, credit cards, etc will wash up. when this happens (most) family members that are holding on to these crazy conspiracy theories will finally let go of them