Linus Torvalds put out Linux 3.15-rc4 on Sunday as expected. He noted in the release announcement that nothing unusual went on in the past week and overall the activity is about normal for being about half-way through the RC releases.
There are some open issues still pending with the Linux 3.15 kernel, but Linus says, "on the whole things are fairly calm and nothing horribly scary. We're in the middle of the calming-down period, so that's just how I like it."
Torvalds' Linux 3.15-rc4 announcement in full can be read via the Indiana LKML archives.
The Linux 3.15 kernel should be officially released in late May or early June and will present many new features with Linux 3.15.