They will work fine as long as we keep trac running. AFAIK there are no plans to turn it off (but maybe should prevent the creation of new tickets?).
So what would replace this very valuable function?
Possibly github's issue system, if we decide to use it. I was assuming in my last mail we were going to start using it, but I'm not sure if that has actually been decided. IIRC there was some resistance because it's a closed system. Maybe this is a subject for another thread.
It's probably worth mentionning that we could also import trac tickets/history/file attachments/wiki into redmine, which integrates decently with git repositories and github. I have used different setups in the past, from github being the central repo with a push hook on github that told our redmine server to fetch the last changes, to a redmine-centric workflow where with the help of some plugins users can add their ssh keys to their redmine account and it uses project rights with gitolite, automatic git repository creation on project creation, etc (basically like github, except it's redmine). Not saying this is what boost want, just saying it's an alternative to managing issues on github. Also Trac supports git since a while now, but I think Trac is slowly becoming obsolete. Philippe