I would say "Yes" just to be safe. It really doesn't matter what others did because their situations might be different than yours - just not the status but others.
Selection doesn't guarantee approval. Also, I have seen rare cases where your H1 gets approved but change of status gets denied. In this case you have to go outside and re-enter with h1 visa stamping. If your both- H1 and Change of status gets approved it only starts from month of October. I know you probabaly are coverede by CAP gap rule even though u don't extend your OPT, but I am not sure what are the rule these days. Please verify. ALso I don't know when your current OPT expires. If you have time then I would say wait for decision before filing extension. If you didn't hear by 1-2 week of August, I would say "Yes". In rare cases u don't get h1 approval even by October. IN my case i got my h1 approval in April of next year.
Hope this helps..