There will be read-replicas, but an ETA is currently unknown. You can do your own caching in the wor
There will be read-replicas, but an ETA is currently unknown. You can do your own caching in the worker via the cache api

What’s next for D1?
We’re setting a clear goal: we want to make D1 “generally available” (GA) for production use-cases by early next year (Q1 2024). Although you can already use D1 without a waitlist or approval process, we understand that the GA label is an important one for many when it comes to a database (and as do we).
Between now and GA, we’re working on some really key parts of the D1 vision, with a continued focus on reliability and performance.
One of the biggest remaining pieces of that vision is global read replication, which we wrote about earlier this year. Importantly, replication will be free, won’t multiply your storage consumption, and will still enable session consistency (read-your-writes). Part of D1’s mission is about getting data closer to where users are, and we’re excited to land it.
— https://blog.cloudflare.com/d1-open-beta-is-here/

workers-types, which includes everything in Workers (and Pages Functions)