Your last sentence got my attention, hence I bolded it for reference. No, don't think it will make much impact whenever (if ever) Facebook comes out with a cryptocurrency. It will just be up in the media with much noise just like Electroneum did when it was launched, that's all. By the way, what is Facebook share worth in the stock market? Just a mere > $100+. Nothing more. If we were talking about a cryptocurrency from Amazon, then I could say, yes much impact.
Even Amazon coin will not make much impact too, same as Facebook, the only impact they will have is to add to the general market capitalization, because most of the coins they will produce will basically be stable coin, which will only be useful for their internal operation.
Although their announcement may make people start rushing to buy bitcoin thinking it will cause pump in the price of BTC, there might just be a little coincidence then, because FOMO will make others follow them in also purchasing bitcoin. So I still think it will indirectly have very big effect on the value on bitcoin. Anyway, the third quarter is almost here.