The beauty of a roadmap is that you know what to expect.
I cannot find Scott's roadmap post, so here are the most important things that I would like to see in the core:
1. Userids in user URLs instead of only username URLs (stackoverflow is using userids by a reason, no confusion anymore with changed usernames, that got stored in the database etc.): /userid/handle
2. List of Comments for each user (requested so many times also as issue on github)
3. Complete move to Jquery, removing all onclick and inline javascript
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4. Possibility to define flexible theme options in admin panel (instead of hard-coding them in qa-theme.php)
5. Base Theme functions for "Ask" page
6. HTML Emails
7. Sitemap splitting if 50k+ entries (sitemap index file) → Done by Ultimate SEO Plugin
8. Reasons for flagging (very often requested, here and on other forums) → Meanwhile I have developed a plugin for this: https://github.com/q2apro/q2apro-flag-reasons
9. Option to disable hotness calculation / hot page
Version 1.8.0 was already a big step! And there is more cool things to be implemented that make life easier :)