Plans to convert Mozilla to the Firebird engine has been been delayed, if not canned. The new roadmap extends Mozilla Suite through version 1.8.
There are factions within Mozilla.org that are pulling development in different directions. One faction believes that Firebird is a faster and better browser. Another believes that the Mozilla Suite code can be reduced in size to make it faster and even more stable than it currently is. These are my views, not those of Mozilla.org.
I have tried Firebird several times yet have always migrated back to the Suite. Plans to continue development of Firebird and streemlining of the Suite can only mean good things for the user. Both are superior to IE.
New Roadmap: Those that follow the roadmap know that the dates are optimistic.