In fact, they MUST co-exist. The plain truth is this: You’d have a very difficult time pulling them apart.
The line between digital and conventional is already very blurry. To wit:
Is a TV commercial delivered over a cable or satellite conventional marketing? Is the same commercial delivered over an Internet stream digital marketing?Is a piece of marketing collateral that is printed conventional marketing? Is the same piece of content posted on a web site digital marketing?Is a chat with someone in an online forum digital marketing? Does continuing that conversation face-to-face mean that chat is actually conventional marketing?Is an e-mail invitation to a trade show booth digital marketing? Is staffing that booth conventional marketing?Is speaking live conventional marketing? Is the video recording of that presentation on a web site digital marketing?