Last time this topic came up on HN, someone linked to a thread on tb-planning where the post-XUL future was discussed. IIRC the "slow rewrite" was considered unworkable, and the proposed plan was to restart from scratch using "web technologies" while continuing doing basically security updates for the classic XUL TB until the replacement is ready.
As an aside, what "web technologies" exactly meant wasn't discussed. Is it electron? Or something mozilla-based like the servo + browser.html experiment? Or running a separate server process and connect to it using a normal browser (like e.g. mailpile does)?
The only feature I find annoying is the search feature, which seems to be a universally accepted weakness of Thunderbird.
Who wants an email client that uses 600 MB RAM just to open and that eats 100% CPU to animate your email folders?
I never really found the conversation view of email very useful (especially if there are more then two people participating in the conversation). It's hard to tell who replied to whom and you can't really get context if there are responses to multiple parts of the message they're replying to.
I do have a strong preference for the threaded view that Thunderbird has now.
Gnus nnimap provides a threaded, conversation view. It's almost definitely not what you'd consider a 'modern UI,' but I like it quite a bit.
The Thunderbird Council is optimistic about the future. With the organizational question settled, we can focus on the technical challenges ahead. Thunderbird will remain a Gecko-based application at least in the midterm, but many of the technologies Thunderbird relies upon in that platform will one day no longer be supported. The long term plan is to migrate our code to web technologies
Mozilla dumps XUL tech from gecko left and right, removed proper "classic" mod support from Firefox... how is this a bright future. Thunderbird as a big XUL app is stuck with an soon to be not supported old gecko. And how is the plan to slowly rewrite it viable? Replication of the dated UI with HTML5 will be an even bigger clusterfxxk.
We need a proper open source offline client. And it should have a modern UI with at least conversation view like Gmail. Wasn't there a HTML5 based email client in FirefoxOS. Start with that code and set up a new Mozilla foundation funded offline email client, and keep security support for Thunderbird until the new email app is ready.