Effect of information on stock indices
If you believe the efficient market hypothesis, then the answer is no;

At the moment relevant information (say, which allow the company to be added to the index reveal, the stock price would automatically reflect the price as if it was already added to the index, as otherwise there would be arbitrage closable by buying the stock at this moment and selling it when the ETFs are getting in.

In practice, I've tried it a few times myself but it seems that in general the market already takes future ETF investments into pricing quite well.