Plone 5.1.5 has been soft-released. Please give it a try and let me know if there are any critical issues. http://dist.plone.org/release/5.1.5-pending/versions.cfg
For those who haven't run across soft-releases before, this is the
last step before the final release. Because things haven't been
finalized yet, some packages may change between now and the release. It
is not recommended to use soft-releases in production.
Looks good. I've sucessfully updated two projects.
for moving out of pending.
@esteele I realeased plone.app.locales 5.1.12 compatible with Plone 5.2a2 and 5.1.5. Be sure to include it, thanks.
Seems fine so far. Tested with some light editing.
I've removed the pending tag and passed the release on to the installers team.
Late to the party, but just asking here: plonetheme.barceloneta (released by @mauritsvanrees) is an alpha release, might that be a temporal glitch? Should we bump that to a final 2.0.0? 
It feels wrong to have a final release with an alpha version pinned there.
another one: plone.recipe.zeoserver was bumped from 1.4.2 to 2.0.0, on its changelog it mentions that only ZODB > 5 is supported:
Does that mean that up to 5.1.4 ZODB <=5 was fine but now with 5.1.5 ZODB > 5 is mandatory? That might be a bit of a too much bump for a maintenance release, isn't it?
Good point. I have just released 2.0.0.
A bit late to change the actual versions.cfg of the release.
The versions.cfg of Plone 5.1.0 already pins ZODB to 5.3.0.
So in order to use an older ZODB on Plone 5.1, you would already have had to downgrade this ZODB pin manually. I would expect problems running buildout then, but if someone has actually done this, then with Plone 5.1.5 they would simply have one extra package to downgrade (plone.recipe.zeoserver down to 1.4.2.).
So seems okay. 