I know some people on this list have been developing tools. There is also a session on manuscript encoding going on.
Since this is the first TEI meeting to have a conference type set of sessions, we are quite keen on getting good papers in--and can afford to be a little gracious about deadlines.
Let me encourage you to consider submitting abstracts on markup if you have some interesting ideas--it ain't every day one gets an audience of people who *want* to hear the gory details of your encoding, after all ;)
If you have an idea for a markup paper but don't know where to submit, let me know and I'll help you find the right person.
-dan