Scheduled FOR or IN the next days

Solution 1:

The relevant usage chart...

(There will be valid alternatives such as scheduled across or during (some future time-span) that simply don't occur often enough to show in a chart like that.)

I see no reason to suppose differences in intended meaning¹ might affect the choice of preposition. It's effectively a stylistic choice, but learners (non-native speakers) should probably stick to the most common (for).

¹ Apart from @anotherdave's somewhat contrived difference when using to schedule as an "active" verb, whereby The timetable for the June exams will be scheduled in the last week of May would become nonsensical if we changed in to for.