Rich doesn't seem to plan anything special (or at least doesn't want to tell us that he does). He got asked this on Twitter and answered:
Quote Originally Posted by Rich Burlew
Posting it shortly after 999 and not long before 1001, hopefully.
Similarly someone asked "Any ideas for projects after OOTS?" which Rich answered with:
Quote Originally Posted by Rich Burlew
Many, many ideas. None that I can share now. Some are already in the works (tho shelved while I finish Kickstarter work).
Whether or not these projects are in any way OotS-related I can't tell, but even when the OotS-storyline ends, Rich can still tell stories in the OotS-verse (like prequels or side stories). I think he will tell us something when he is ready/able to do so, but I wouldn't suspect any announcements in the near future, since Rich said that there will be 7 books (so 1.5 to go).