I strongly believe that if some well known investors come in and buy billion dollars worth of bitcoin it could be world breaking news and the price of bitcoin would soar high to $10000, just my opinion.
Well if these investors that you speak of will buy billion dollar worth of Bitcoins then they are enough to push the price so much high. Imagine the amount of Bitcoin they bought, and based from the law of demand and supply, this will greatly lift the price. Reaching 5000 USD would be instant and within just few weeks or months, 10,000 USD will be undoubtedly reached.