There will most certainly be another beta release. WWDC isn’t until June 22nd, it’s late this year. Last year we were testing 12.4 in May/June, and prior to that was 11.4.1 beta, and in 2017 was 10.3.3 and 9.3.3 in 2016. We even tested 8.4 with the new music app design leading up to WWDC 2015.
As much as some people disagree on this forum, Apple loves receiving feedback from its beta testers. Three weeks with no feedback/bug reports is a long time. The last time we were not testing a beta when WWDC hit was in the iOS 7 days. We tested iOS 8.4, iOS 9.3.3, iOS 10.3.3, iOS 11.4.1 and iOS 12.4 in the weeks leading up to WWDC. All these updates went public in late June/July/early August.
On top of iOS, every macOS release since El Capitan saw a 10.x.6 update released in July. Since Catalina is still not up to quality standards, I see no reason not to see another macOS update. Since a new macOS update needs to be tested, they will release corresponding betas for iOS, watchOS and tvOS as well.