Eoan is open for development, whilst we still wait for the animal portion of the name. Here are some transition plans for this cycle:
gcc-9 as the default gcc.
glibc 2.30 when it becomes available in August or later.
python3.7 as default and supported, with python3.8 as simply available in the archive. As the 3.8 final is too close for the 19.10 release. The plan however is to have python3.8 as the default and supported in 20.04 LTS.
Speaking of python2 
hopefully, it can be demoted from Main to Universe this cycle. We are currently left with deja-dup/duplicity (port completed upstream), heartbeat (pacemaker v2 stack doesn’t need it), mailman3 is getting promoted to main this cycle, and OpenStack Swift. I am not sure where the latest status is on OpenStack Swift, but hopefully, we can get Swift to move to python3 this cycle.
Also hoping to switch default/only implementation of bzr to the python3 port breezy 
.
icu transition to 64.2 or newer. And we also need to backport support for the new Japanese era Reiwa (令和) into stable releases. Not sure how that will be done yet.
⬣ boost transition to 1.70 or newer. Mostly to get better compiler support.
OpenJDK 11 as default, with 8 & 13 available.
golang updated to 1.12.
on installer front, we are aiming to bring the new server installer for all 64-bit architectures: s390x, ppc64el and arm64. Also a slight change on x86 platform is to use 
vmlinuz & initrd symlinks in /boot, rather than in /.
Please note that 
Debian is 
frozen, thus there shouldn’t be too big of a flood of updates/merges initially… But there might be a lot of things landing if Debian releases in the next 6 months. And it’s time to start thinking about landing things for the next LTS release, as you might want to get stuff in this cycle, for things to be polished in time for 20.04 LTS!