Oh no, plenty of users will try and go more than 3 levels deep and then blame the theme for being inadequate. Users will try to add sparkles and ponies to their theme and blame you for not having a sparkles and ponies feature built-in (you know, because everyone wants that and if you don't add that feature they'll tell the world just how awful you and your theme are).<br>
<br>Whenever you have a user-base (in anything) expect to take all kinds of bizarre abuse. The only difference is those that are willing to educate their users and those who aren't. Is it even required to support one dropdown level as long as he explains in the read me that it doesn't?<br>
<br>The point is that if you only add 0-2 dropdown levels you're constantly going to have to explain to users/customers why it doesn't support more. They won't even see this as a "design choice". Psychologically, they'll just see the theme as broken because it doesn't do what they want, probably even give it a low rating because of some trivial thing that didn't meet their exact specification.<br>
<br>Pessimist? Nope, realist. Welcome to WordPress.<br>