It's highly likely this is a good thing, we won't know until we see them. If you're accustomed to referring to one of the existing guides you may want to visit the site and download it before it disappears.
Here's TNA's blurb about the new look guides:
The in-depth research guides are intended for experienced researchers who need detailed information on how to find and understand records relating to particular subjects. They cover a huge range of subjects, reflecting the vast and unique collection held by The National Archives. The in-depth guides complement the shorter research signposts, which are intended for users beginning their research.
The key changes to the in-depth research guides include:
Researchers should also note that the guides will no longer appear as results of searches specifically within the Catalogue, but they will continue to appear as results of searches of the whole website.
- a new look, to bring the guides into line with the rest of the website
- quick links to other relevant guides to help researchers move more easily between guides on related subjects
- a quick link to the Catalogue
- improved printing and pdf options
Work is continuing to update and improve the content of the guides themselves, to make them more suitable for the needs of experienced researchers. As part of this, a number of guides on similar subjects have been merged, and a small number have been archived.