Paradox, I know John is extremely busy and doesn't get onto the Chrons as often as he'd like these days.
With that in mind, I'll answer in his stead, if that's okay.
This is a little unusual but not unprecedented by any means. With a major publisher, you can expect a gap of anything from one to three years from a book's acceptance to appearance.
Smaller publishers are normally a little quicker than that but by no means always. It depends on
how small they are and how much they already have in the pipeline. For example, Pete Crowther's PS Publishing, which is a veritable giant among small presses, typically has a lag of a couple of years simply because of the amount of titles they're considering and accepting. Others may only publish two or three titles a year and already have several in the queue. For my own NewCon Press, I have two short novels which have been sitting in files for six months and I haven't even had a chance to consider them yet (but then I did warn both authors it would be this summer before I could).
I'm afraid that when it comes to getting your work published, you sometimes just have to be patient. It's your call whether you accept the delay or choose to look elsewhere.
Having said all that, congratulations on getting an offer in the first place!