Who's putting their bets on Microsoft going open source with Trident and Chakra next? Spartan is an opportunity for them to clean up the mess before releasing the codes I think.
At least for Chakra, this would make a lot of sense - I can't think of a downside for them. For Trident there is the theoretical downside that IE becomes fully independent of Windows. This currently doesn't matter, but might decrease lock-in in the future.
Windows dependency of IE is one of the worst things about IE - like having to restart your PC to update your browser. What year is this again?
The fact that it was stagnant, ubiquitous, limited to Windows, and encouraged ActiveX were the major issues, since it made it more difficult and expensive to develop and transition to web applications for about a decade.
Windows will automatically reboot every 6 weeks anyway once evergreen Windows 365 comes out.
I've been thinking that Spartan will probably go cross platform at some point, an opportunity for them to get a few more Microsoft accounts created and it's not like it being Windows only is going to convince people to switch.
I don't know about "Trident" but I think EdgeHTML and Chakra might become open source. I remember reading some where that they were looking into the pros and cons of doing that.
I like IE's dev tools, but my main platform is OSX. Their memory profiler stuff is pretty sweet. If the community could help them maintain builds for other platforms, I would rock that.
My bet is on Chakra, once open-sourced, becoming the JS backend for Node enterprise.