When Google rewrites a title tag, the impact on search rankings is difficult to predict with certainty. However, it's generally recommended to place the most important keywords closer to the beginning of the title tag, as this is often seen as a stronger signal to Google about the content of the page.
If Google decides to rewrite the title tag and places the brand name first, it's possible that the SEO impact of the original version may be reduced. However, it's also possible that the rewritten title tag may actually improve the page's search visibility by making it more relevant to certain search queries.
Ultimately, it's important to remember that Google's algorithms are constantly changing, and there's no guaranteed way to predict the exact impact of any particular change. However, by following best practices for title tag optimization, such as placing important keywords closer to the beginning of the tag, you can help ensure that your page is well-optimized and likely to perform well in search results.