"Do you believe that the value will increase or decrease?"
Translation:Tror du at verdien kommer til å øke eller minke?
kommer til å = you're talking about something that is out of your control, e.g. the weather, the price of gold etc. It's very common in speech, because obviously lots of future events are out of our control!
skal = something that you have a firm plan or intention to do, that is within your control, e.g. going to the cinema, booking a holiday etc.
This is in Norwegian, and goes into more detail: http://grammatikk.com/pdf/Futurum.pdf