The deprecation notice is added to the docs and deprecation warnings are raised during usage of the functions. As per the PR some of them are deprecated with 3.8 (master) and will be removed by 3.10. But this depends on the discussion over the deprecation cycle. There were cases in the past where issues were raised in bpo for undeprecation (issue27172) after being deprecated for several versions. There are also cases where the functions that had to be removed were postponed for removal to a later version instead of the one initially shown in warnings.

# Python 3.7 no warnings

$ python3.7
Python 3.7.1rc2 (v3.7.1rc2:6c06ef7dc3, Oct 13 2018, 05:10:29)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from gettext import NullTranslations
>>> NullTranslations().lgettext("test")
b'test'

# PR branch

(pr_10139) ./python.exe
Python 3.8.0a0 (heads/master:4e3a53bcee, Oct 26 2018, 23:44:23)
[Clang 7.0.2 (clang-700.1.81)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from gettext import NullTranslations
>>> NullTranslations().lgettext("test")
<stdin>:1: DeprecationWarning: lgettext() is deprecated, use gettext() instead
b'test'


Hope it helps