It's your choice to wait till the new model comes out. Some people hold off right till they release the next model. It's your money thus you have to spend it how you feel best. I wouldn't hesitate to recommend the Mac mini but if you're waiting for the new one it might not come till 2021 or 2022 since they're not on a regular update cycle.
I ended up ordering the macbook 13" 10th gen model. I figured the switch to ARM would take some time to get all my software over so no need to wait for WWDC.