Whedon said that he wasn't really interested in producing the series anymore. He wants to focus on the next two movies.
That's not true. If you're referring to the Entertainment Weekly magazine, it was taken out of context. Whedon is looking at expanding both the Buffyverse and the Fireflyverse, he's just a little booked atm.
By the way, the same wit that's in Firefly is in Buffy/Angel. The problem with such a long-running show like those two is a lot of people (I did this) watch a few episodes in the middle and judge it. The attraction of Whedon shows is your attachment and reactions to the characters, and you really need to start at square 1.