Project Electrolysis*[
1] (multi-process architecture, sandbox)
Project Quantum[
2][
3] (the goods of Servo[
4] project)
WebExtensions[
5][
6] is the only supported standard for extensions
Some work was done on UI and it is called Photon UI [
7][
3][
8]
and for Windows users:
Firefox is finally going to update* from 32-bit version to 64-bit version on 64-bit Windows OS
*Partial implementation was shipped in current or previous releases