Im casting doubt on them doing 4K re-renders. At best it will be 4K recompositing for shots that are simple composites. I doubt they will be re-rendering any complex CGI.
All non-CGI shots have been scanned in 4K from the original negatives, and all CGI shots have been scanned in 4K from the original VFX film-outs. So yes, the CGI remains 2K (although scanned in 4K), but I believe it’s at least been re-composited with the newly-scanned 4K footage. So overall, it should be a nice uptick in quality!
That is, as long as they didn’t majorly eff up the color grading again! IMO, this NEEDS to have an HDR grade that’s very much in the spirit of the original theatrical/DVD look (although with higher dynamic range and a wider color gamut, of course). If it has a new revisionist grade – or if it has a stupid, dark green grade again – then I’m going to be pissed.