The Symbian Foundation has released its roadmap for the rollout of the upcoming open-source versions of the Symbian platform and expects the first devices based on the next platform to launch before the end of the year.

“These packages are finding their way into platform releases. The plan is that there will be two platform releases each year,” said David Wood, Symbian’s executive vice president for research.

Based on S60 5.1, Symbian^2 will reach a functionally complete state by the middle of this year and should be hardened by the end of the year, he added. As a result, the first devices based on Symbian^2 could reach the market sometime around the end of 2009 depending on the integration plans, the level of customization, and the design choices made by manufacturers.

Symbian^3 will follow six months later. According to Wood, it will reach a functionally complete state by the end of this year and should be hardened by the middle of 2010. The Symbian Foundation also expects Symbian^4 to be functionally complete by the middle of 2010 and hardened by the beginning of 2011.

During all of the rollout processes, platforms grow as contributors add features prior to functional completion. Between the “functionally complete” and “hardened” stages, the development community improves platform stability by testing and contributing defect fixes. Once it is hardened, the release enters a more stable phase.

Package owners will continue to incorporate contributed defect fixes for about 12 months, but the prime focus will shift to later releases. Contributions from the community will govern progress toward the “functionally complete” and “hardened” milestones. Typically, the Foundation expects to see five platforms under development at any one time.

“The intent is to ‘timebox’ each release by fixing the functionally complete date and including only features that deliver in time at a reasonable stability level,” Wood said. “This is the same principle that has worked so well with integrated releases of Symbian OS in recent years.”

Symbian^2’s feature set is “already virtually frozen,” Wood said. While most of Symbian^3’s content has been agreed upon, there’s still some scope for contributors to make a difference. The content for Symbian^4 and future releases is still open.

“In many senses of the phrase, we’re open for contribution!” Wood said.