Agreed. SPECTRE ends in a way that it actually could close Craig´s tenure. Storywise, however, BOND 25 could (and IMO should) finish Craig´s tenure better. After that, in BOND 26 he would be the oldest Bond since Sir Roger - and I don´t think that Craig wants that, and neither would the youth-obsessed studio heads that cough up the money.
So, IMO, there will be one more Craig-Bond if everything goes according to plan (EON definitely wants to hang on to Craig). If not, BOND 25 will start fresh.
Either way, the next year will be very interesting, laying out the deciding factors: 1) SPECTRE´s worldwide grosses (right now, it seems to come out of the gate very strongly, but will it have staying power?), 2) Which studio will be the next distributor (if SONY continues they will want to hang on to Craig as well since he is a proven commodity in Bond films).
If the grosses will come in significantly under SKYFALL (look at the comparison between THE AMAZING SPIDER-MAN and the much costlier THE AMAZING SPIDER-MAN 2), it might be construed as a reason for another reboot (not of the origin story but of the conception of the films, including lead actor).
And if WARNER BROS. (reportedly the biggest competition for SONY on this) takes over it might very well start fresh, just because that´s what happens when another business force takes over.