I assume you're just asking about Glee's status, not the story lines, right?
If you want info on the story lines, let me know more specifically what you want to know about those and I'll tell you. Otherwise, here's the 411
There IS going to be a season 4.
They are
currently on season 3. This season goes until May. Then we'll have summer hiatus, and season 4 will start in mid to late September.
Now, as for the status of characters in season 4.
There will be new characters in New Directions. There are eight characters on the show right now who are seniors and will be graduating. That means that, unless glee changes their show's rules for show choir competitions, New Directions will need to add at least four more people. (They need 12 people, total, to compete in sectionals/regionals/nationals)
This is assuming that everyone not explicitly stated to be graduating at the end of the year sticks around, which they might not. If that's the case, they could need as many as nine new characters, but I doubt that will happen because that's a lot of people to bring in at once, halfway through the series.
Of course, this is just looking at who's graduating and who isn't. But surprise surprise! Some of the characters that are graduating will STILL be on the show!
The following is a post I made in a different thread.
garra_eyes
All of the senior are graduating, but some of them will be staying around next season with some "revolutionary" (the network and cast's words, not mine) idea for the show.
Seniors who will be for sure staying on the show (but who may or may not be staying in Lima): Kurt, Santana, Finn, and Rachel
Seniors who are (as of right now) leaving the show: Quinn, Mike, Puck, and Mercedes
Juniors who will likely be sticking around: Blaine, Artie, and Tina
Unknown: Brittany (It has been hinted that Brittany might fail all her classes and be held back, but nothing has been confirmed), Sam (He's a junior, so one would assume he would stick around for next year, but he's not a series regular yet, so we don't know for sure), Sugar (same reason as Sam, except she might be a sophomore or freshman), and Rory (as an exchange student, who knows how long he'd stay. Plus, as a Glee Project winner, he has already gotten more episodes than he was promised, so who knows if they'll continue to keep him around or bump him off).
So, that's where we stand right now on what characters are going to be around next year.
Blaine, Artie, and Tina will still be in New Directions. Sugar and Sam probably will be staying as well. (unless the actors decide to leave the show, I can't imagine the writers would get rid of them and then have to go through the trouble of finding even more new and unfamiliar faces to add to glee club next year) Rory and Brittany... who knows? Part of me thinks the writers would keep them around so that they don't have to overwhelm the audience with too many new people in season 4, but I really have no idea what their plans for those two are.
And then there's Finn, Rachel, Santana, and Kurt who will be... off doing something, probably in New York, but still on the show.... Somehow... Or maybe they'll stay in Lima and do something. That part's all a big mystery right now. All we know is that we'll get to see them in season 4 as regulars.