Two different points in this short mail:
-the two new strings (from partman-auto-lvm package) may now be translated. Be aware that the "Use free space for Logical Volume Manager" must be kept SHORT (less than 70 characters, I'm not sure of the exact limit now) which may be tricky if you want to avoid jargon (and you MUST avoid jargon....remember that D-i is targeted at all users, not only geeks)
-you can make updates in other translations but there's not guarantee they will make it into the packages. Packages belonging to the initrds (mostly those involved in early stages, before the CD-ROM detection phase for cd-style installs) have already been uploaded.
So, though cleaning out your work is always good, this work is more for the future than for the release.... (yuck, my English sucks)