1 Billion USD will hugely pump the btc price, maybe double the price to 1100 usd. Maybe even higher, I don't know because I have no so much money.
Then it'd come straight back down with a even lower price than before. Pumping is never a good idea and I do not recommend anybody tries it, as you are going to lose money, even on altcoins. Crowd funding is totally different from this scenario. Because lot of people will not pull of their investment at a single time. So, slow and steady will make bitcoin more stronger.