Don't Wait If You Need a Phone Now
Don't wait if you need a phone right now. There are so many excellent options available and the Pixel 4 is still pretty far away. If you're needing something now, it'll be worth it to buy a phone today, then maybe trade it in for the Pixel 4 later. Especially with all the trade-in deals available these days.
Whether that's the OnePlus 7 Pro, a Galaxy S10e or even an aging Pixel 3 XL. The Galaxy S10+ is amazing, too, not to mention you can choose between two screen sizes with the Note 10 this year.
In fact, I'd argue you should get the Pixel 3 XL right now, enjoy it for a few months, enjoy the just-released Android 10 software, then DON'T buy the Pixel 4 when it gets announced. Instead, wait 3-4 weeks after the Pixel 4 release date for Black Friday and holiday deals, then trade in your Pixel 3 XL for a discounted Pixel 4 XL and reap the benefits.
Seriously, that's a great approach to take.