My H1B is expiring this september and I am going for the stamping next week. Should I make my dependents visa also stamped next week? If I stamp it next week and incase if he couldnt travel till september, will I be able to file extension for my dependent from US itself? or should I stamp it after the extension my H1B visa?
If your dependents do not plan to travel till Sep, then there is no point of them getting the visa stamped now.
You alone can go for stamping, and once you land in US and get your petition extended, they can go for H-4 stamping.
If they plan to enter US w/ you, then they should go for stamping now. When your extension is filed in US, you can include them as well (only if they are in US w/ you).