But, how would one replace a desk phone or handset with another icon? A picture of the smartphone on the desktop isn't right. And, the idea of hanging up a phone to end a call is equally obsolete for many.
There are other categories which are on their way out, even if not there yet - a picture of an envelope for mail, a physical book for an address book, and a manila folder for the concept of a directory (which word also reflects an obsolete concept).
And then, there's the LWN icon, a penguin holding what I can only imagine is supposed to be a newspaper.
These will all likely to be around even after no one remembers the physical artifact. After all, people still "dial" phone numbers, even though most young people have never put their finger in a hole and rotated a dial clockwise. Of course, those numbers are only dialed when communicating with someone not in the phone's directory.