He's a Lieutenant Commander. Although not promoted for Nemesis, Sisko specified it was unlikely (but he didnt say impossible) he would be offered a command of his own for chosing his wife over his mission. Given his service since then, he could be considered "redeemed" and be promoted and or given a command of his own. In the non canon TNG relauch his is promoted to first officer, in Countdown to "Star Trek" he is a General. Keep in mind he frequently commanded the Defiant and several missions for both Starfleet and the Empire, both Sisko and Martok trusted him .
Sisko's opinion about Worf was obviously not everybody's opinion.
The devil is in the details. Sisko said he would probably never be offered a command on his own. Having a command is not the same as being of the rank commander. A commander rank is the navy equivalent of a lieutenant colonel in the army.
Sisko clearly said "probably never" and "given command", not "never" and "promoted". This desicion is a major plot point in the novel Resistance, where he turns down an offer to be PIcard's first officer after Nemesis due to that scolding Sisko gave him.