The kernel in F7T1 already supports ext4 filesystem but the userspace does not seem to be there yet. As ext4 is very important in order to address the scalability requirements of large storage systems, this should happen for F7.
No chance. This isn't going to happen until upstream removes the 'dev' moniker. Whilst there remains a possibility for the underlying filesystem metadata to change, we can't risk putting out a release which may leave end-users with unmountable filesystems. It'll get turned back on for rawhide after F7 goes out. Enabling this in F7 would be utter madness.
The F7 kernel tree has the ext4dev filesystem... emphasis on dev. It is still incomplete and in experimental state, just for the record. Also while the ext4dev code is in the kernel codebase F7 uses, it is not actually built in F7. This is all still very much in development & in flux - perhaps down the line in F7 updates we can enable ext4 in the kernel and in e2fsprogs, but it's clearly too late for the initial F7 release. e2fsprogs is trickier than the kernelspace change, due to the fact that we cannot regress e2fsprogs by introducing the ext4 changes.
see also bug #338391 for the anaconda side of this. Still no ext4-capable e2fsprogs to package anywhere, I'm afraid. upstream e2fsprogs is moving slowly and "ext4 capability" for e2fsprogs is essentially a bunch of patches in email archives at this point.
EXT4 is in F9. Can this be closed?
Yep.