I have not upgraded yet from 7.7.1 > 7.7.2
Now that I read above about the 7.7.3 fix I'm thinking of waiting since we have 10000+ members
So should I wait for 7.7.3 or do the 7.7.2 upgrade anyway?
Go ahead and upgrade anyway. As this issue only affects a single script when being used to search members in the administrator control panel as 1/ "search without entering any search terms" and 2/ "search members by email address." Everything about 7.7.2 is an upgrade or fixes multiple other issues.
If you cannot wait until 7.7.3 is released, and absolutely need to "CP: Admin > Member > Search By Email Address", you can probably use the /admin/membermanage.php file from 7.7.1 (i've not tested this).
UBB.threads 7.7.3 includes substantially updated Admin > Member Search code and results page.