L2 extension based on my I-94 or I-129?

[jgg]

I have a valid L1-B and I-129 petition valid till Sept,14 and my I-94 expiry date is April, 2016. My spouse I-94 expired in Apr, 14 and I had applied for her extension by filing I-539 in March this year based on my 1-94. We haven't got a decision yet and are expecting our first child in sept, 14.

We have got a clean record. What is the likelihood of her I-94 getting extended? Is it based on my I-94 or my I-129? I am also going to file for I-129 extension soon. Please advise