The next three major versions of Flux, Fluidpages and Fluidcontent are coming along nicely. Release is not long away.
Work on the new major versions is going great and we are getting very close to finally making the release. If you wish to try out the new features the Git master branches are all stable enough to use - at this time they contain all the promised features with their final API being stable. Minor kinks are still being worked out but it's nothing that should prevent operation.
There will be a fully detailed upgrade guide coming at the same time as the releases, but for those of you feeling brave or just curious, here is what you can do to upgrade your site to the Git masters (which will be fully replaceable with TER versions once released, with no further need to perform upgrading):
If you also use either one or both of the fluidpages_bootstrap and fluidcontent_bootstrap extensions you should of course also update those to the git masters. As with flux, fluidcontent and fluidpages, these two extensions will also be directly replaceable with the coming TER versions.
Be aware though that fluidpages_bootstrap, because it misses an update script, will lose connection to the currently defined page variables - I recommend you only perform this update on testing environments (or be prepared to either reconfigure your pages, or take advantage of the fact that fluidpages_bootstrap now features TS options to configure every page variable - colors, sizes etc).
It is of course also recommended to update VHS to the Git master version if you perform the other upgrades described in this article. In general you are much safer using the Git master version of VHS than any of the other extensions - the VHS ViewHelpers' surface API is perfectly stable and by far, the majority of changes which happen in VHS are additions and bugfixes (not affecting the attributes and thus not risking breakage).