Season 8 Timeline
It would make sence to have more than a couple of months between the end of Season 7 and the beginning of Season 8 if what we've seen so fai in the way of previews hold true. There would have to be some sort of training period, allowing Buffy and Company to move into what appears to be the high tech world they will now occupy. A year would seem to be the very minimum time required for such an undertaking, and if the logistics of locating, training, and directing the now "thousands" of new Slayers in the post-Chosen world. Five or six years would seem more logical.
As for what happened after the Angel finale, anything that large couldn't possibly go undtected by the new Slayer/Watcher community, so SOMEBODY would have followed up on it. Whedon has said that he does have plans to have both Angel and Spike in the Buffy series, but not in extensive rolls. (that would mean, I fear, no closure to the Spike/Buffy/Angel issue, which might mean yet another new boyfriend for our favorite Slayer).
The one thing we can be assured of about the whole thing is that the new series will progress SLOWLY, with a (hopefully) monthly installment consisting of only a few pages of material at a time. We had all better be prepared for what will probably be the equivalent of a single one hour episode drawn out over three or even four months, which means that if this consists of a twenty to twenty two issue run, about half a dozen "real" episodes. The possability of a Season 9 will be a long way in the future.