Unfortunately the opposite is also true, there are also some problems in plone.app.contenttypes that would go into a release at the moment if it is released and included:
This improvement/fix in plone.app.contenttypes breaks a default and custom mosaic templates in plone.app.mosaic:
Layouts and default_pages are not correctly migrated in plone.app.contenttypes, existing issue but could have more impact after another fix done in march:
Link CT links with navigationroot variable substitution are broken when the site is accessed through VHM after a fix to support urlparams in the link.
B: "Layouts and default_pages are not correctly migrated"
The march commit is already part of plone 5.1.2 (p.a.contenttypes 1.4.10)
So making a CMFPlone release using 1.4.11 would not change anything (would not make the situation worse)
C: Link CT broken:
Is broken in 5.1.2 (p.a.contenttypes 1.4.10) so making a CMFPlone release using 1.4.11 would not make the situation worse.
Conclusion:
If we use the already released 1.4.11 of p.a.contenttypes we do not make the situation worse.
If we release and include 1.4.12 we do make the situation worse.
Of course unless we can fix these three issues - but I suspect it could take time.
A) I have no idea. A migration would fix shared layouts, but not layouts stored on filesystem in add'ons. After this issue I learned out that mosaic layouts are non trivial and broekn anyway as soon as you use anything 'non' transient in p.a.mosaic 2, so I'm not sure if this really is a 'big' issue, but it's still annoying and might be a red flag for more knowledgable developers where the Marker Interface clean up/fixes might cause problems, I don't know.
I'm working on getting packages released this week, so get your PRs in! If we wait too long, the sprinters are going to make my life miserable next week.