Patrick has just finished uploading his latest work for Slackware-Current branch that indicates next development cycle for next Slackware release is now officially started.
In this batch of update, he upgraded GLIBC to 2.19 and the Linux Kernel to 3.14.3, the latest version available at this time. There are several new packages as well in networking area, such as libnftnl and nftables which is the future potential replacement for iptables.
There's also a fix on bash-completion so that it's working well with newer bash 4.3.
I still don't see GCC gets upgraded at this time, but hopefully GCC 4.9.0 could make it into -current soon.
Start your current engine and start testing guys :)