Think very carefully about whether you want to work for a company that asks these and other well-known ridiculous interview questions. If you really need the job your best bet is to try to gather some insider information and tell them what they want to hear. Otherwise something you make up on the spot is as good as something you've genuinely thought about.
What did they plan ahead, their answer, their improvisational skills, their lying ability or the job they'll be doing? Better hope it's one of the first three.
The company can't in fact make those kind of long term plans any more than the employee, so it indicates that the company/interviewer lives in a fantasy world. Damn why did we hire all these people who only wanted to grow technically and now we need people managers? We hired all these people and they said they wanted to grow technically, so the next person we hire must be someone who wants to be a people manager. Luckily no-one ever changes their mind and the company knows exactly what it is going to need in five years.
But we've had this argument on this forum before and it's clear some people will cling to the "Where do you see yourself in 5 years?" cult no matter what.
I think people also cling to the cult of The Employer is Always Right and HR is Good For Me.
HR should pay me my salary, thats it. HR should not be involved in anything else - least of all, hiring decisions.