Homicide is more like a prequel - the source material is the same as The Wire but was developed a decade earlier.
WOTC is indeed a follow-up of sort (same author as The Wire, produced recently), but the real follow-up to The Wire (i.e. what David Simon did straight after, bringing with him a bunch of actors from The Wire) was the short-lived Treme.
There's also The Deuce more recently. I found it excellent, though the subject matter (sex work and early 70s/80s porn industry) probably will turn a lot of folks off.
The real prequel is The Corner, which features a bunch of the same actors sometimes on the other side of the law.