Wait for More Information
Again, at this stage, we don't know a whole lot about Apple's plans. That said, if you're interested in a new version of the iPad mini, you might want to hold off on buying a new iPad for the time being.
If an iPad mini 6 is coming in late 2020 or 2021, we'll likely hear a lot about it before Apple makes the official announcement.
You can expect rumors and leaks to outline the device's potential features (3.5mm headphone jack, 5G support, etc), and a potential launch date, well ahead of time.
We should also hear more about the other iPad models Apple's planning. Again, the company is reportedly developing a new budget iPad with mini-LED backlighting and an iPad Air 4 and these would be a top, in-house competitors for the iPad mini 6.
If the device is on track, we expect rumors to pickup during the summer and fall and those rumors will help you make a more informed decision about your next tablet.