Tobi's eye is connected to obito.
Tobi however is *not* obito.
Facts are when Tobi attacked the 4th hokage (minato). Kakashi was young and Obito around same age. Also declared dead by this stage.
Kabuto when he 1st found tobi. Said he had a good host(something along those lines).
Now i could imagine his eye survived in the other dimension for a while and some wack story will be told how tobi achieved it.
But if obito is tobi i will be pissed off due to the time line not fitting. Why not just make the uchiha invincible otherwise.
P.s i dont like making guesses but i would like to know what happened to the girl from that group (kakashi, obito, forgot the girls name, minato).
Right there with you.

I think most people keep forgetting certain facts in their excitement. The timeline for certain things just doesn't fit with Tobi being Obito. I've posted this before but I think it's necessary to post it again with the buzz that this new chapter has created....
I've been seeing a lot of people mention the Minato vs. Tobi encounter while making an argument for or against Tobi being Obito. I would just like to point out three things. Firstly, Obito was only 13 when he was crushed by boulders. Not only was his right side crushed under the initial avalanche of falling rock, but the rest of his body was buried during a second cave-in. Kakashi and Rin saw this take place.
Secondly, Tobi's age is all wrong if he were to be Obito. Going on the fact that Kakashi and Obito were about the same age when Obito died, and by calculating how old Kakashi was when we were first introduced to him in Part 1, we can assume that Tobi's attack on Konoha with the Nine-tails happened a short time after Obito died (probably not long after the Third Ninja World War ended). Kakashi and Obito were both 13 when Obito was killed and Kakashi was 26 in Part 1 of the manga, meaning he would have still been 13 (possibly nearing 14) at the time of the attack on Konoha. Obito would not have been able to grow up that much in such a short period of time. If you look at pictures you can clearly see that 1) Obito is shorter than Minato and 2) Tobi and Minato are around the same height. So both the age and height difference are something to consider.
Thirdly, Obito loved Konoha. Why would he suddenly want to destroy it? It would be a complete 180 degree turn around of his personality.
Sorry for this being another "Tobi isn't necessarily Obito" post. I just felt like I needed to point all that out again. It'd be more feasible to me if Tobi was using Obito's sharingan.