firstly nextrelease is a bad name - i should rename is current-stable-release or something similar that makes more sense
to answer the question in the heading: trunk will become nextrelease once its released - the current nextrelease will be decommisioned once trunk is ready
to answer the question in the post - work on trunk as that is what is in need of alot of attention
we've got 2 separate streams of development - nextrelease (current-stable-release) for minor patches (though i did break that rule by creating the extension system here :) ) - and patch release done from here - trunk - for major work that will be release in the future
i'll try and re-setup and action list of stuff that needs to be done for trunk in the next day or so - refer: -- http://www.simpleinvoices.org/roadmap -- http://www.simpleinvoices.org/roadmap/trunk