So NTTD is supposed to be the final Daniel Craig film, and definitely seems like it's being advertised as a finale, continuing and probably concluding some of SPECTRE's plot threads.
So question is, what happens after? Should the series once again reboot the continuity? Although Casino Royale did give the initial impression it was a soft reboot by keeping Judi Dench as M, later films made it pretty clear it wasn't with new takes on Q, Moneypenny, Blofeld etc. The other films of course frequently recasted but sort of had a light continuity (Bond's marriage being brought up a few times for example) up until then.
They could go that route with Craig, recast Bond but perhaps keep Harris, Fiennes, Whishaw etc...or start from scratch again. Although many wish for Idris Elba, he's 47 and probably be nearly 50 by the time the next Bond will probably be made. Age of course, famously became an issue with Moore staying until he was nearly 60, and it could be argued it sort of was an issue for Connery in his last two films as well.
Maybe start from scratch? Cavill I can almost see; he read for the role in Casino Royale but was considered too young at the time, and his Superman was iffy but he seems to be doing quite well with the Witcher, who has some of the rawness of the Craig era Bond. He also already has done a few spy flicks, much like other Bond actors have before they were cast.