If I remember correctly, it was just some study by one muslim scholar, so it's far from being "officially declared" for all muslims in the world. Some other scholars might even later declare it haram for some reasons. But regardless, I don't think that it will have any significant impact on Bitcoin's price, those muslims that wanted to buy Bitcoin earlier most likely did it regardless of its status and Bitcoin is also not that popular in arabic countries to make a big impact on Bitcoin's price, just like bans in some countries have almost no effect too.