Many of the comments to the Thunderbird / mail post include suggestions about features for Thunderbird. These range from topics like adding visualization to adding calendaring functionality.
I encourage people to take these topic to the Thunderbird development and discussion areas. I would say the same thing if the topic was Firefox. Feature and product planning happens within the project group. For example, there are many comments about calendar functionality, and there is an active calendar project underway. The Thunderbird discussion areas are the right place to ask about the roadmap for integrating Lightning into Thunderbird, to note the degree of need and to look for a timeframe. Better yet, that’s the place to get involved in making things happen. Mozilla is successful when we are rooted in active, distributed involvement and contribution.
If it turns out that there is some barrier to getting involved, or if there is some other problem for contributors, then we’re in a different place and I definitely want to know about that.
I suspect most of us agree there is a lot of exciting potential improvements for Thunderbird and for mail in general. The point is how best to get sustained, focused attention and real movement to addressing these.