Assuming you mean beer (ie once fermentation has taken place) rather than wort (unfermentted), then yes you can leave it and carb later although a blast of CO2 to ensure its sealed up and not leaking is a good idea. Every so often I leave mine for up to a month or so before carbing up as the keezer is too small. You could prime in the keg in the mean time
Is there a reason not to add CO2 immediately? You purge O2 and prevent oxidisation, you seal the keg, you get it started on carbing.. I can't imagine why you wouldn't unless you didn't have the CO2 immediately on hand, in which case, leave it in the fermenter where there is likely a layer of CO2 produced during fermentation which is protecting your beer from oxidisation.