From my reading, context and interpretation were two domains that IBM specifically had to target with Watson [1], to get it to process natural language. If Jeopardy is solved, legal advocacy might be a next harder problem?
Like Jeopardy, the task involves a lot of "soft" information, but results in an easy to measure pass/fail decision. It could be run in real-time, as an advocate in a courtroom, or off-line as a legal adviser. Also like Jeopardy, it offers the opportunity of a public contest, and the associated PR.
[1] http://www.research.ibm.com/deepqa/faq.shtml
---
Edit:
It seems like at least one person inside IBM is already thinking this way. To quote [2]:
"Law, Patent and Trademarks"
"Not only could a Watson-like capability minimize filing through existing databases on laws, prior cases, rulings, hearings, opinions, it could also be used as a method of testing witness questions. or suggest a series of inquiries and questions for litigation. It could be used to simulate certain judges, prosecution and defense lawyers, based on prior cases."
"A Watson-like system could generate questions for a prospective patent claim based on it's ingestion of the entire patent and trademark database."
[2] https://www-304.ibm.com/connections/blogs/davidian/entry/whe...