Until We Meet Again
In the U.S., this book may be part of the Last Apprentice series, but it's hardly the last book. As of May 2013, there are a whopping twelve books in the series, plus two companion books. Joseph Delaney obviously wants you to read more of his books, so he leaves a lot of plot threads dangling at the end of Revenge of the Witch.
One reason we know there's more to this story is that Tom's still the Spook's apprentice. He's just not Spook-y enough yet, we guess. It's a given that he's going to be cavorting around the County with the Spook—perhaps to some of the locations we've heard about but haven't seen yet, like Anglezarke Moor—and will do battle with more vicious boggarts, a witch or two, and maybe something we haven't even heard of yet.
We can't forget about Alice, either. Tom sure won't. His last line is, "I was feeling lonely already" (14.127).
Even if we hadn't peeped online that there's a book called The Last Apprentice: I Am Alice, we'd be pretty sure we'd see her again. Too much is made of her character's dilemma—is she good, bad, or something in between?—to leave her behind for good. We just hope we don't have to read ten more books before we see her again. For our sake, and for Tom's.