The latest Ask HN post on developer laptops is dated now[0]. As of now the haswell processor coupled with Intel HD 5000+ looks like the way to go.
Options I have looked at(If you have information about pricing/release date on any of these, leave a comment)
1. Macbook air: Average display, no option to upgrade ram
2. Sony Viao Pro: Reviews say it compromises on performance to be the lightest.
3. System76 Galaga Ultra Pro: Any first hand reviews on this one?[1]
4. Lenovo T440s: Release date unknown, 6 hours of battery life only[2]?
5. Samsung ATIV Book 9 Plus: Would be overpriced, QHD+ would be overkill for my needs!
6. Dell XPS 12: Not a fan of convertible tablet + laptop types.
[0] https://news.ycombinator.com/item?id=4860540
[1] https://www.system76.com/laptops/model/galu1
[2] http://shop.lenovo.com/fi/en/laptops/thinkpad/t-series/t440s/