Since Ubuntu sync most of the packages from Debian, I took a look there, and saw that icu version 1.53.1 has been packaged in Debian experimental. See https://tracker.debian.org/pkg/icu for more package information.
However, if you look under "testing migrations" on that page they are planning to transition to the new version. In practice this means that any package depending on icu in some way are rebuilt with the newer version to make sure they still work as expected with the newer version. See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=757025 for details. ** Bug watch added: Debian Bug tracker #757025 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=757025 ** Tags added: upgrade-software-version -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to icu in Ubuntu. https://bugs.launchpad.net/bugs/1371588 Title: 53.1 is out and contains many bug fixes and new syntax Status in “icu” package in Ubuntu: New Bug description: That's all really. They're saying it's much better than 52. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/icu/+bug/1371588/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp