I guess you ask since you will be interviewing for one of the digital practices -e.g., McKinsey Digital-.
Most of the cases you will have to facewill be "normal" ones. Normally, each interviewer has his/her own case that they repeat candidate after candidate. Hence, when you are interviewed by a generalist -that you will, at least some of them- the case/topic is completly regardless of who you are and what your background is.
However, it´s highly possible to get one interviewer who comes from the Digital Practice -altough this doesn´t have to guarantee that he/she makes a digital case-.
Hope it helps!