Even if they could bring him back, there really isn’t anywhere to take his tenure beyond NTTD. They’ve already pushed things as far in the sci-fi direction as I think the tone of his films would allow. Even if you worked around that and pulled a FYEO with the next film and brought things back to earth, you still have to explain how he survives the end of NTTD. Even though the ending of that film leaves quite a bit desired and it’s not particularly well executed, it’s still pretty final in what it presents to the viewer. There’s not much, if any, wiggle room to explain away somehow surviving a rocket to the face.
Craig was a brilliant Bond, right up there with Dalton as one of the very best, but it’s time to move on. Hopefully bringing in a new actor will ignite the creativity of all of those involved and we get a return to form film much like we saw with the debuts of the previous three Bond (CR, GE, and TLD). I would say the odds of us getting a good film are much higher with a new Bond coming in fresh and with no storyline baggage to deal with rather than trying to continue to further examine the convoluted storylines that they were really leading to nowhere really fast by the end of SP and heading into Craig’s finale.