I'm no pro on the synopsis... but from what I understand (and I spend way too much time reading up on these things) you have more lee-way in a synopsis than you do a query as far as sharing that info. Recently I'm also seeing more and more that agents mention they want to know if a story has series potential - as long as first story can stand on it's own.
If it's me - I'd add something about the series - but I'm pretty sure there are more qualified opinion givers on this topic.
In a query letter you can mention series potential. I would not do it in a synopsis.


