It would be, if that were what Lewis intended with the series. And though he may have started the story thinking this was going to be a one-time toss-off for his goddaughter, by the end of it he was clearly thinking otherwise. (Remember the Professor's words - "Once a king in Narnia, always a king in Narnia"?) It seems even at that point he was envisioning follow-up stories.
I can't say that I understand why the lamp was dark at the end of the story, and I don't know if Lewis thought it through that clearly. It may be that the lamp had "done it's job" in guiding the children to Narnia, but that wouldn't seem to square with the "accidental" creation of the lamppost in Magician's Nephew. It wouldn't seem that it was "created" to do anything - it just happened.
For my sake, I'd have a hard time reading any significance into the dark lamp at the end of the story, other than Lewis not dotting all his 'i's.