During Nintendo's E3 2019 Nintendo briefing, it was announced that Banjo and Kazooie are joining the roster of Super Smash Bros. Ultimate.
The trailer was brilliant, in that it was a rollercoaster of emotions. First, we thought we glimpsed the silhouette of Banjo and Kazooie; then, it was revealed to be Duck Hunt Dog with that stupid duck on his shoulder; and finally, the true pairing was revealed.
This has been something that fans have clamoured for for a long time, and it means a partnership, however briefly, between Rare and Nintendo. The trailer is actually called 'Best Friends,' which I think refers to the old partnership.
Phil Spencer has been open to it for some time; this Tweet dates back to 2015, for instance: