It can be predictable but not always but only if you found great project coin which is like example here in signature campaign then it would be great project,if coin owner advertise hard that coin,also buying top trending coins and sell later is really great strategy and really predictable.
We cannot know the exact amount but the market experts can predict based on the data they have if the price will going to rise or not.
The one that price depends is the number or users who are willing to buy is I think that is more unpredictable that is why trading is so risky. We cannot really tell the exact.