You can wait for ages or simply build it on your own.
Just in case you have a build system ready ...
git clone ...openwrt...
cd openwrt
git pull
git remote add satura https://github.com/sartura/openwrt
git fetch satura
git checkout satura/ipq40xx-dsa
./scripts/feeds update -a
./scripts/feeds install -a
make menuconfig
Change "Target System"="...ipq40xx"
Subtarget=generic
Target Profile=Asus RT-AC58U
And don't forget to include LuCI if you want to ...
Worked fine that way on my FB4040
Cheers,
Thomas