Wait for Better Performance
If Apple is working on new iPad Pros for 2020, you can count on them to include a variety of performance upgrades.
A report from Bloomberg claims that the new iPad Pros will unsurprisingly come with "faster processors" which we assume means they'll come equipped with Apple's A13 chip. This will help them standout from the 2018 models.
The current iPad Pro models, and the iPad Air 3 and iPad mini 5 for that matter, pack enough horsepower for most people, but if you aren't satisfied with what's out there, think about waiting.