No, its not. They just do stuff like that to reference other seasons. And although this isn't the same thing as what your talking about, a lot of voice actors do more than one season.
Did you know Takuya and Matt have the same voice actor? As do Ken, Veemon, Impmon, Dynasmon, and too many others to name (maybe another time )
When season 8 comes, (huge spoiler alert) they summon the heros of the past, the characters from past Digimon universes, to come to the Fusion universe and help fight evil. It's only for a few episodes, though.