From the new TV Tome,
www.tv.com, is the list of all episodes:
51: North by North Quahog 5/1/2005 4ACX01 2 reviews 8.6
52: Fast Times at Buddy Cianci Jr. High 5/8/2005 4ACX02 1 review 7.9
53: Blind Ambition 5/15/2005 4ACX04 7.9
54: Don't Make Me Over 6/5/2005 4ACX03 10 reviews 8.6
55: Stewie B. Goode (1) 0/0/0 4ACX05 6.1
56: Bango Was His Name Oh (2) 0/0/0 4ACX06 6.7
57: Stu & Stewie's Excellent Adventure (3) 0/0/0 4ACX07 6.7
58: The Cleveland-Loretta Quagmire 6/12/2005 4ACX08 19 reviews 6.3
59: Petarded 6/19/2005 4ACX09 23 reviews 6.7
60: Brian the Bachelor 6/26/2005 4ACX10 19 reviews 6.1
61: 8 Simple Rules for Buying My Teenage Daughter 7/10/2006 4ACX11 7.5
62: Breaking Out Is Hard to Do 0/0/0 4ACX12 6.7
63: Model Misbehavior 0/0/0 4ACX13 7.1
75: Patriot Games 0/0/0 4ACX25 0.0
In bold are the episodes that were aired already.
There are 14 episodes in that list, three are out of order, they are all connected (1)(2)(3) and are now the movie.
There will only be 11 episodes for season four
Season 1 had 7 episodes
Season 2 had 21 episodes
Season 3 had 22 episodes.
Season 1 and 2 were bundled together for the DVD. Season 3 was sold alone. I assume that season 5 (which was picked up already by FOX) will have 11 to 14 episodes, making 22 to 25 episodes (when combined) for a DVD box set.
As you see, there are only four more episodes this season, three after next week (no eppy tomorrow

).
Then, it will be the summer schedule, which translates to RERUNS, and then season 5.
Hope this helps!