All indications are that Microsoft Office 2008 and 2011 applications will run under Lion (they are all universal binary).
Office 2011 has an Intel specific installer, so it can be installed under Lion.
The original 12.0.0 Office 2008 installer however requires Rosetta, and since Lion drops support for Rosetta you won’t be able to use it to install Office 2008 under Lion. You will need a later released Office 2008 installer to avoid this requirement.
So if you plan on using Office 2008 with Lion, and you only have an original installer, make sure it’s installed prior to upgrading to Lion… and hope you never need to reinstall it!