we decided that it doesn't make sense to keep xp supported, nobody has such a system anymore, qt itself (angle) doesn't support it, so it might be more and more problematic to keep this running.
Not completely decided yet, it makes sense for packagers of single applications, krita/calligra might still not benefit though.
There is some discussion going on whether to have stable branches at all. This might not be needed for our applications in the common installer, some things might become different though for packagers of single applications; especially adding new dependencies and bigger internal changes might bring serious problems in a faster release cycle.
likely to come soon. Patrick wants to set up at least one machine, and if we get access to some windows licenses, we might even be able to install some VMs to increase speed and extend coverage.
As said before, we need the discussion about future branches Aleix mentions that projects can explicitly state if they want to support a platform.