As of today in LibreOffice Git is the initial AArch64 support. Over one thousand new lines of code were added to LibreOffice by Red Hat's Stephan Bergmann for allowing the open-source office suite to build on the ARMv8 64-bit architecture. LibreOffice already runs on many CPU architectures from x86 to Alpha and SPARC with ARM64 just being the latest.
The initial support for 64-bit ARM will be found in the upcoming LibreOffice 4.4 release. LibreOffice 4.4 is expected for release in early 2015, which should end up panning out fine given that aside from select seeded developers and other stakeholders that it will still be months before seeing Linux-friendly 64-bit ARM development boards (or products) out in the wild.