Just taking some notes here on the ones I know of, so we can continue discussing and planning:

How much traffic does the wishlist generate?

I assume we mean all visits to:
https://meta.wikimedia.org/wiki/Community_Wishlist and its subpages. (after they are deployed)

How many people click to open the intake form?

Count if visits to: https://meta.wikimedia.org/wiki/Community_Wishlist/Intake

How are they submitting wishes? Is it the form, or wikitext, or something else?

The form us accessed through the above URL that runs gadget that opens the form vs. click on "Edit Source"

What is the form completion rate?

Assuming validation succeeds and submit button (copy might change) in the bottom left is not greyed out and button can therefore be clicked.

Which wishes are seeing the most engagement? (pageviews/comments)

All wishes from this list, have a wish page, each one has it's own talk page
https://meta.wikimedia.org/wiki/Community_Wishlist/Wishes

Which focus areas see the most engagement? (pageviews, comments, votes)

The complete list of focus areas can be found here:
https://meta.wikimedia.org/wiki/Community_Wishlist/wiki/Community_Wishlist/Focus_areas
Each one will have a talk page and votes visibly displayed.

Open question:

• are we also tracking editing existing wishes?

After conversation with Connie we know that to be able to track comments and votes on wishes and focus areas are hard to track in our case. The best way we can do it is to add specific edit tags for these events. e.g add edit tag "focus-area-voting" to edits that add {{Support}} template to focus area talk pages; and add edit tag "wish-comments" on edits that comment on wish pages