Let me provide an insight about the new estimate experience, mathislandscapes.
You can see a NEW badge (top left of the page) when you click the +New button and select Invoice or Estimate. And, the badge is only available to new QuickBooks Online customers or subscriptions.
See the attached screenshot below for your visual guide.

We are on a journey to migrate customers to the new invoice/estimate experiences for the web and mobile. This migration will be the first phase of moving existing customers to the new experience.
The customers in this phase have a basic setup (one template, no sales tax setup, no classes/locations). As the invoice product team builds new enhancements/features, more customers will be migrated.
You can browse these links for additional information about the new experience:
Let me know if you have other concerns aside from getting the new estimate template. I'll be right here to provide some insights about the update.