I was invited to speculate. Here's where logic takes us (not very far, I'm afraid, but it's a start):
The idea that a debris field was created in the SIO - and yet the world's collective search efforts have yet to identify a single ounce of it - is well beyond the bounds of common sense.
I concede that the search area is vast and inaccessible, and that, over time, debris sinks, degrades, and comingles with other junk. But all of those things take time; and many items (lifejackets, eg.) retain their visibility, flotation, and evidenciary value for years, so all that would have been needed to positively identify something was a sufficiently vast and hi-def satellite search.
I distinctly remember watching a televised news item about new technology that allowed satellites to read the headline on a newspaper held by someone on the ground. They used "newspaper" instead of "iPad", because the item I watched was broadcast in the 1970's. So I'm going to go out on a limb and suggest that current satellite technology is sufficient to scan quickly for possibilities, and zoom in to identify.
So here are the 3 possible avenues taken by the investigation leadership over the past 5 months:
#1 they decided to withhold this search technology (i.e. chose not to find anything)
#2 they applied the technology, found debris, kept it secret, yet still haven't found MH370
#3 they fully applied the technology, but didn't find debris
#1 requires either irrational search leadership, or the known non-existence of debris.
#2 requires irrational search leadership.
#3 requires the non-existence of debris.
Result: if the search leadership is rational, then there is no debris.
The southern-track-until-fuel-exhaustion hypothesis requires debris (a powerless 777 cannot magically "self-Sully" onto a rolling, roiling ocean).
Result: if the search leadership is rational, then the southern-track-until-fuel-exhaustion hypothesis is invalid.