The best replacement for trac is bugzilla.

The best alternatives to trac are rated as following:
★★★★★  bugzilla
★★★  redmine
★★★  mantis
★★★  jira
★★  reflex
★★  select trac
★★  ridgeline
★  command trac
★  quadra drive
★  bloodhound
★  atrac
★  gitlab
★  selec trac
★  github
★  apache bloodhound
★  nissan frontier
★  limited slip
  cell tech
  fogbugz
  gforge
  roundup
  long trac
  quadra trac
  quadra-trac
  rock trac
  oe spectrum
  track lock
  gas magnum
  otrs
  kyb
  honda ridgeline
  short trac

Your alternative for trac is not listed? Suggest!
Speaking about trac, one probably shouldn't forget about multiple projects.

Other search terms related to trac and their ratings are:
★★★★★ multiple projects
★★★★ subversion
★★★★ visualsvn
★★ mod_wsgi
★★ multiple repositories
You have in mind a companion for trac and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of trac in all years. Click on graph for more.
trac
bugzilla
redmine