Some experts think that till the end of this year the price of Bitcoin will be 15000$. May be they have a lot of Bitcoin and just want it. That is why "predict" it

Exactly. Many predictions just express the desires of these predictors. But neither these predictions, nor desires do not affect the market.
Some believe that until the end of the year, the price may fall to a level of $ 1,500, others believe that the price may rise to $ 22,000 this year.
To be clearer, I suggest that it is better for you to follow the development until the end of the year because it is very difficult to predict the price, but if I personally think this year is quite difficult to see prices going up
In the open spaces of the cryptocurrency market there are different situations. Who knows, perhaps the market will please us before the new year with a bitcoin price of 22,000. But I do not believe in it.