POSSIBLE SPOILERS AHEAD
Timeline: Middle of series (major revamp)
Character Changes: Maria Deluca is dead, Michael was never with Maria, Tess is dead. Michael and Isabella are together.
Recent Story Developments: Michael's fiance died, Michael & Isabella recently got together. The lot are all in Hell on Earth
Michael Guerin's ex fiance was the daughter of Elijah Mikaelson, so first highly notable crossover would obviously be with The Originals. After that, would no doubt follow Hell on Earth, as that is currently where the group is currently settled.