No. It does not work that way. Photo Stream is temporary, and should not be used to store photos. There is no secondary storage when the photos are removed.
Photo Stream is meant to make it easy to get to recent photos from several devices and computer. It has never stored all your photos.
The only exception is if you are using Photo Stream with a computer. Unlike mobile devices, the catch on the computer is not limited to 1000 photos. I twill continue to grow until/unless you delete them yourself. It is still not wise to trust this. Save important photos elsewhere.
The only photos backed up in iCloud are the ones in your Camera Roll; the ones currently in your Camera Roll, not a history of photos there were on your Camera Roll. And you can only restore them by restoring the entire iPad.
iCloud: Photo Stream FAQ
Always, always, save your photos off the iPad if you intend to keep them. Either online, or on your computer. Preferably both. Even if you are storing in them in a third party app. Mobile devices like the iPad are subject to 'bad things'. Nothing important should ever be trusted solely into their care.