I think ultimately the wreckage of MH370 will be found.
Advances in undersea technology, better ROVs, the insatiable nature of human curiosity and the fact that the truth seems to have this habit of eventually emerging all suggest this will happen. It just doesn't say when it will happen. Whoever made time, made plenty of it.
If Robert Ballard can find the "Titanic" and the "Bismarck" (admittedly both had reasonably well-documented surface positions), sooner or later someone, probably looking for something entirely different in the Indian Ocean, will find the images of a wrecked airliner marching across the screens.
There are far more people who have an interest in finding the wreckage than are interested in not finding it for reasons best known to themselves.
I have no doubt Boeing, for example, would like their aircraft to be absolved of any fault or blame due to a defect. If the cockpit section (or whatever remains of it) is unburnt then the fire in the electronic bay theories go out the door. Perhaps the FDR will be recovered to tell its story. Will the CVR be of any use? Perhaps, perhaps not. But when the wreckage is found, forensic investigators will find enough evidence to eliminate the wilder theories, and those that remain will boil down to one which is the best fit for the available evidence from the wreckage, some of which will almost certainly be recovered and brought to the surface for closer examination.
Eventually, the truth will emerge. But it may take another decade, or two, or more. The evidence is there; it will be found.