So, two major theories about the next Halo is that Master Chief is back on the Ark, and the Forerunner automaton rising out of the sand is Mendicant Bias.
First, let's address the idea that the construct is in fact Mendicant Bias. I'd first like to show all of you how people reached this conclusion.
Bits and parts of other quotes were used to also justify the fact it is Mendicant. However, these quotes are taken out of context.
Here's a section of the full passage:
Those arms referenced earlier were in fact actually dock arms used to recieve descending ships. Later in the section, Mendicant Bias is actually described as being an oblong of silver metal. Later in the passage, he is entombed under the sand in his oblong coffin. So unless that coffin can transform into a 50 foot mechanical bird....
Also, here's the icing on the cake:
Obviously, these land formations were not present in the background.
Now, to address the idea that Master Chief is possibly back on the Lesser Ark...
First off, I'd just like to say, I think the Ark Theory is the best theory we have right now and the most likely to come true. But, there are some inconsistencies.
This picture shows the interesting similarities between the Teaser Trailer, and the Lesser Ark as it appears in Halo 3.
Everything seems to line up. But, if you notice, the planetoid in the Teaser hasn't been as mined away. Secondly, there's actually an in-game view of the planetoid standing at the edge of the Foundry.
This is the planetoid when you stand at the edge of the Foundry.
Half the planet is submerged by mists and clouds, while the other half is a considerable distance away. Now, even if the firing of the Halo knocked the planetoid out of it's original spot, it wouldn't look as big as it does if the planet we see is in fact the planetoid at the Ark. Especially since Chief is nowhere near the edge of the Foundry if he's on the Ark.
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In conclusion, I do think Mendicant Bias will play a major role in the Reclaimer Saga, and there is a good chance we will return to the Lesser Ark since the Excession at Voi was reactivated, and an expidition team went through to recover 343 Guilty Spark. The popular theories may have the right idea at what's coming up, but they make too many far fetched and unrealistic conclusions.