h4 to h1b COS, I94 expiring soon.

Current VISA H4, valid till September 30th, 2017, I94 valid till the same date.
before to H4, I was on H1b, still 3 years left for H1.
Got another job and company is applying for H1b COS from H4 in the regular processing in mid of September as there is no premium available and plan to convert it to the premium as soon as it opens.

My question is that if in any case (worst case scenario) my h1b COS gets denied, then what option I will be left. Shall I apply for H4 extension too? if yes then two petitions will go together, H4 extension and H1b transfer, what will be likely scenario?