The eventual approval of the COIN fund is obviously likely to increase the price.  However, the magnitude of the increase does not seem so easy to predict.  Some complicating factors:

(1) I expect that, at first, the fund will buy the bitcoins that it needs from the Winklevosses and other investors like Tim Draper (and the eventual DPR  coins auction).  That is presumably why the Winklevosses are after that fund.  So the demand on the exchanges is likely to be indirect, from people who expect the price to rise because of the ETF, rather than from buys by the ETF itself.

(2) Granted that SMBIT and PBP are less glamourous than COIN, but they do not seem to have had much success, or much effect on the price.  SMBIT holdings have grown only 2000 BTC, from ~105 BTC to ~107 BTC, over the last two months.  They grew ~30 kBTC from December to April, but the price dropped almost 50% in that period.   

(3) Bitcoin's only intrinsic value is its utility as a method of payment.  Its value as an investment depends entirely on that utility.  Bitcoin is a high-risk invstment because no one can tell what the demand for that use will be, and there is a positive probability that such demand (and therefore its value) will go to zero at some point.   Approval of the ETF will not affect the expected demand for that use, nor that probability of failure. Therfore COIN shares will be just as risky an investment as bitcoin itself.  If large institutional investors do not trust bitcoin now, why would they trust COIN?