So, a couple things wrong with the current addition:

1) I think you meant `wp_get_current_user()` -- `get_current_user()` is a PHP function that does something related to the server.
2) `wp_get_current_user()` returns a user object, not a string, and as such can't be concatenated onto a string.
3) Even if it could be concatenated, you should sprintf it into the translated string, you should never use a variable or function inside a translation call.
4) Also, missing the textdomain.