And about things being too obvious... well, you have to think that Rowling came up with these ideas over a decade ago, long before she had fans who could figure out what was going to happen. But people have been analyzing these things for so long that they're bound to eventually stumble onto a real idea. Think how many people guessed that Dumbledore was going to die in Book 6.
If RAB is Regulus Black, then he won't be able to get the other horcruxes in book 7. He's dead.
I seriously think that the final book will take place almost immediately after the end of the previous book (i.e. June or July 1997) for two reasons.
1. It will be kind of hard to call Book 7 "Year 7" if it takes place in some other time frame.
2. Since Harry said he was only going to stop by the Dursley's just for one last recharge of his love protection and then immediately start on his quest, it seems like extremely important parts of the story would be lost if we skipped a year or two years or whenever after Dumbledore died.