Well anything's possible, but that would be a risky strategy. The deed is signed. The only leverage that shareholders can exert is to vote against the deal. If the deal is voted down and St Gobain doesn't come up with more money then CSR goes back to $7 and First Sentier lose their lunch money.
In my opinion, it's much more likely that First Sentier are taking a position to cash in on the difference and will use their stake to ensure that the deal proceeds.
CSR Price at posting:
$8.84 Sentiment: Hold Disclosure: Held