If Nintendo were any kind of smart, it's a Diddy Kong Racing. There's also a lot of reasons to believe Retro is making it. Think about it.
1. Retro have pretty much become DK series developer and have proved they can do the property justice.
2. The Kart racing genre is still pretty big. DKR was able to get half of MK64s sales back in the day. If a new one could get even half of MK8's sales itd be a huge success.
3. Retro helped with MK7. While not entirely strange, it definitely makes you think why they were asked to get involved in a genre they have never worked on.
4. Maybe co-developed by Monster? I think there was once a rumor that Excitebots was supposed to be a DKR sequel and they havent put anything big out in a while.
5. Diddy Kong was originally planned for MK8... but was cut.
Diddy Kong is not a stranger to the MK series, so it's unusual that they chose to cut him despite showing him off as part of the game.
The new trademark is just icing on the cake.