We are about 9k away from 50k.
The game is called Warhammer 40,000 because it takes place in the 41st millenium. The events of the Gathering Storm take place during the 13th Black Crusade, which by the Imperial calendar is 999.998.M41
In other words, it is taking place at the end of the 41st millenium. So if the timeline does advance, then the calendar would change to 000.000.M42.
So are we moving into 50k? No. Are we moving into 41k? Yes.