i might be going on a limb on this, but is it possible that tobi's warping jutsu has something to do with the rinegan's deva path ability. we know of the shinra tensai and the bansho ten'in which repulse and attract things. at the same time, when used together, we assumed it causes a third jutsu which is the chibaku tensei which creates a black hole. what if the chibaku tensei's black hole if manipulated in another form of jutsu can be the portal that opens up to that other dimension. since its principle is the same as the shinra tensai and bansho ten'in, it would explain why there is a 5 second interval before the jutsu can be used succeedingly. but like i said earlier, this is a very far fetched theory and not really a high probability of being true.
I think now might be an opportune time to remind people that I have always been in the camp that Tobi is really -somehow, in some sense- Obito. Just in case his mask finally gets shattered some time in the next chapter or two and it turns out I'm right, so I can say "CALLED IT, BITCHES!"