Halo has already been treated by different studios(Halo Wars and the mobile/VR stuff) and also Bungie and 343 while share a lot of employees are different studios.
343 can and should continue with Halo but would be cool to see them do something new after Infinite and let Halo rest a little bit between expansions and such.
Make a spinoff maybe trough another studio, a Horror game with the flood were you’re just a regular soldier or maybe even just a regular human would be pretty cool.
When it comes to GEARS, Coalition is already resting on the franchise and giving it to someone else only makes sense for spinoffs like Gears Tactics, wich was awesome.
Basically do what they’re already doing BUT MORE