回复：You may be lucky - 回复：继续请教863211关于H4的延期的问题:

Most likely the CPB office may not extend their I-94 because they used the old H1 approval notice to enter US before the new H1 extension is approved and the CBP had no fault. Of course if they are lucky, it may work, but it is too risky because the I-94 will expires on Sept. 2, especailly the H1 extension is still pending and not know when will be approved. So, filing I-539 is safer though they need to pay the filing fee of $300.