If Obito, Kakashi and Rin escaped the rock fall that day how strong do you think they would have become? Would they have reached high jonin level or maybe even higher than that?
Well...
Obito would have had two Sharingan with full power to his unique Kamui abilities, with the potential of unlocking Magekyo Sharingan: Amaterasu, Tsukyomi, Susanoo.
Rin would be Jinchuriki of the Sanbi, and depending on her abilites would have good defensive (medical) Jutsu as well as a good offence (power of Jinchuriki).
Kakashi... i am not too sure about. Without the Sharingan he would be unable to master Rakiri. He is a good tactical fighter but aside from his Summons (Ninja Pack of Dogs) i am not sure what his fighting style would be. He would neither be called the 'Copy Ninja'
however he would still be the son of the White Fang so who knows.
Generally, the three would have made a good team, with two stronger and one weaker (as is the case with most Teams of Three in NV).