I am currently trying to figure out how to ask someone what they want to be in the future, as in what do they want to do career-wise. I am not sure which way sounds better. I feel as though the present tense of querer sounds better to me. "What do you want to be?" and "What will you want to be?" are what I translate them to, but I'm not sure if I'm completely correct. I just want to know which would be used more frequently and if I'm translating them in a correct way.
"¿Qué quieres ser?" sounds better to me.
"¿Qué querrás ser?" means the desire is in the future. Put it another way, it would be closer to "What will you want to become in the future?", than to "What do you want now to become in the future?"
When talking to kids, in my country the usual expression is:
"¿Qué vas a ser [cuando seas grande/mayor]1?" => "What are you going to be [when you're older]?" (part in square brackets optional).
Depending on context you might also use some other expressions:
"¿Qué carrera vas a hacer/estudiar/seguir?" => explicitly ask for the career
"¿Qué te gustaría estudiar/hacer/ser? => "What would you like to ...?"
: The choice of "grande" or "mayor" is regional specific. "Grande" usually preferred in Latin America, and "mayor" usually preferred in Spain. (See comments)
As a native Spanish speaker, ¿Qué quiere(s) ser? sounds better.
The future forms of the verb querer are used but not often.
However, I've seen querrá used in other type of questions when a dialogue is involved:
— Hola, busco a Ana.
— Ana, te buscan.
— ¿Quién es?
— Estoy algo ocupada. ¿Qué querrá?
As a child, I was always asked the question as ¿Qué quieres ser cuando grande?
But never was I asked something like ¿Qué querrás ser cuando grande?