New DLC

If I get the latest DLC will it load to the latest patch or will I have to re-patch to the latest patch?

You can just install the latest patch again.
Should save you from any possible trouble.

Please see the FAQ section 3 - page 6 and 7 goes over much of this in detail.

http://www.overflandersfields.com/Downloads/FAQ%20WOFF.pdf

Example..
Lets say your WOFF2 is updated already at v2.16.
You can install Addon1, 2 or 3 fine and you will not need to re-update WOFF2.

However each ADDON has its OWN update, so install the correct update for that ADDON you have installed, once the addon is installed. It will NOT affect v2.16 itself only the files in the Addon!

See the WOFF2 download page.

WOFF1 users can only install Addon1 (again you do NOT need to update WOFF1 to 1.27 again afterwards if it is already updated).

(PS Addons can not be updated on WOFF1 by the way, the new addon updates need WOFF2 features).