Hey @hellokrittech, the Gatsby Image component is indeed now deprecated, but the deprecation has no effect on your site's speed. gatsby-image will continue to work as intended.
That being said, gatsby-plugin-image includes major underlying improvements that provide even better speed. It also plays much nicer with the metrics tested in Google Lighthouse.
Support for gatsby-plugin-image for gatsby-source-prismic is in the works. Bringing in support requires integrating with Imgix's Gatsby plugin, @imgix/gatsby. Imgix is currently working on making their gatsby-plugin-image support available to plugins. Once it's ready to integrate, it will be added in the next major version of gatsby-source-prismic (V4).