There will be no Book 3. There will be some short stories (see the announcement I just posted) but I'm planning for at least most of them to take place in "the past".
Male half-vampires can reproduce, with half-vampires or "muggles" or with mostly-muggle hybrids.
Werewolves can reproduce without help (although they will not activate without any vampires present). A female werewolf who quits her wolf amounts to a physically-25-year-old "muggle" who will pass on wolfiness to all of her children, and male wolves are obviously capable of siring children with "muggles", presumed capable of doing so with half-vampires, and demonstrably capable of doing so with non-active wolves. (Two of the currently-active wolves have a child together from before they activated.)
There is no particular reason why a population consisting entirely, or almost entirely, of half-vampires or other degrees of hybrid-ness wouldn't work.
Can activated werewolves reproduce without help? It seems that sustaining an all-wolf population would require most of the females dying of old age.
This is a thread for discussing my luminous!Twilight fic, Luminosity (inferior mirror here), its sequel Radiance (inferior mirror), and related topics.
PDFs, to be updated as the fic updates, are available of Luminosity (other version) and Radiance. (PDFs courtesy of anyareine). Zack M Davis has created a mobi file of Radiance.
Initial discussion of the fic under a Harry Potter and the Methods of Rationality thread is here. The first dedicated threads: Part 1, Part 2. See also the luminosity sequence which contains some of the concepts that the Luminosity fic is intended to illustrate. (Disclaimer: in the fic, the needs of the story take precedence over the needs for didactic value where the two are in tension.)
Spoilers are OK to post without ROT-13 for canon, all of Book 1, and Radiance up to the current chapter. Note which chapter (let's all use the numbering on my own webspace, rather than fanfiction.net, for consistency) you're about to spoil in your comment if it's big. People who know extra stuff (my betas and people who have requested specific spoilers) should keep mum about unpublished information they have. If you wish to join the ranks of the betas or the spoiled, contact me individually.
Miscellaneous links: TV Tropes page (I really really like it when new stuff appears there) and thread. Automatic Livejournal feed.