Specifically, will LibreOffice version 3.5 be included in Pangolin (12.04)?
but more generally - I don't know how to determine what software packages are present in various Ubuntu releases.
Is that information available somewhere?
You can see package versions on launchpad - for example, here: https://launchpad.net/ubuntu/+source/libreoffice
On the command line:
Or from a precise install - look at the applications Help - About
It will be LibreOffice 3.5.1
More information like this https://wiki.ubuntu.com/PrecisePangolin/TechnicalOverview/Beta2#New_Applications_and_Defaults