At this point doesn't the stratosphere kind of have to be the VZW GSII variant? In my mind it would be almost impossible for Samsung to keep not one, but two phones so heavily locked down. If they were able to keep an entire phone secret from us then bravo, but I really don't see how that would be possible. With that being said, it makes much more sense that they are only keeping one phone secret and that the stratosphere and the GSII are actually the same phone. And seriously... it's called the stratosphere.... They don't really give out bigger hints than that.
That being said, I feel like the Bionic and the Stratosphere being on the same day isn't really that absurd. These are both phones that have had a bit of trouble getting to the shelves and I think VZW realizes that their hand is kind of forced. They probably originally set these phones to launch a couple weeks apart, but I doubt that they were able to keep to their original plans. Since they don't want to put either phone too close to the iPhone release I think they just bit the bullet and put them in the only place they could.
Having pictures of the Celox out and being tested also makes me think that there might be a god and we might get that in the US on VZW (at least in my dreams).
In regards to the slider, I just don't think that the one picture of the slider is enough to say that the slider is even a phone that might come out. It would be a completely different matter if we had consistent leaks of a Samsung slider, but we had a single very blurry picture that is now a month old. As CK said we really don't have any information, but my bets are that the stratosphere and GSII are the same phone and that we will see it in the first week or so of September.