> Some questions: could it be possible to have automatic landscape mode
> for floats depending on their geometry?


What happens is that the float body gets boxed, and the float caption
gets saved as a token register, then in the OR a template instance is
(or more truthfully, will be) called and will have information about
which float area (eg top of 3rd column, right hand page) the current
trial is for, and is responsible for making a typeset box, so it
can attach the caption wherever it wants and can rotate whatever is
needed; and returns a typeset box to the OR.
If the output routine in the end decides to not put the float in that
area, this box is thrown away and the next trial gets the original box
and caption tokens.

> More involved: is there any chance to see automatic `picinpar' (say, a
> float specifier telling: if width < .4\columnwidth, run the text of
> the current par around,

No. Not in the first release at least. As you know tex really can't
change the measure of the galley depending on insertions or page breaks
as it can't unbreak the lines once they are broken. Something could be
done for `here' type floats that actually stop the galley production
but not in the first release (or the second, I fear:-)

> (i'm thinking of these bible editions where
> the commentaries go to the margin next to their calls, and fill the
> bottom (sometimes the top) of the page depending on their length
> relative to the main text's length...

Yes something like that.
Marginal stuff is currently unimplemented (unless Frank has been working
late:-) There was an earlier implementation with a different output
routine, but last month we basically redid the entire OR (again)
and margins have to wait until it is a little bit more stable.