mmm... given that Thor is going to have short hair (Dammit!) probably this is not from the end of the movie, but it may be the post-credit scene for Doctor Strange and still be part of Ragnarok , like the postcredit of Ant-man with Civil War, the newspapers are confusing me, maybe there´s two scenes on Midgard, one about Odín and one about Strange, but yeah, probably they have been on Earth a few days.
hahaha, I thought that too about Loki being bad at lay low, just because he is Loki and have to be always fabulous, specially if the comments about the umbrella that Thor has in a lot of the pictures being Mjolnir with and illusion is true.
Also, there are a LOT of pictures of these two days and the Thor and Loki tags on Tumblr scare me if there´s something like a clue in one of the pics it will ends up in a comicbook blog, I read something about what the people that were these saw, it seems to be an scene where Thor takes a picture with some fans (and it suppose to be part of the movie) and that in other scene Loki creates a portal or some kind of spell and then gives Thor the note, right now I can´t post the links and even if I manage to find them again and post them all of they must be taken with a grain of salt.
About Odin being there, probably he´s being brainwashed, which would be kind of weird, I can´t picture Loki at the end of the last movie defeating Odin, at least without help (if he still had the mind stone maybe... and even with that would have be difficult), there´s also the option of him being in his wanderer mode like the myths, but I don´t think so.
He was potrayed as a vagabond in the Lost Gods arc of the 90´s (but that time was because of a pretty boring villain called Seth) the situation also reminds me to the earliest part of the JMS run
About the comics, the solicitations of November say that Unworhty Thor is a miniseries which is a shame, is that what they have going to do from now on? one mini after the other? it´s not bad I guess... but kind of disappointing, ongoings would be better to complement TMT. maybe it would tie with the main series with the Shiár wars, given that both Thors will be in the space.
Also, you were right and Sif is filling the asgardian slot in the League on the Realms (and Angela the one for the angels) nothing about the Frost Giants (expect a giant finger, that is probably from an enemy like the dark elves)