Character sets in general will certainly continue to grow — look no further than the ever-expanding emoji set. Unicode is designed to be able to incorporate new characters.

Whether the CJKV¹ set will grow is another matter entirely. I expect that there will be a couple more extensions for characters found in historical sources; the goal of the Unicode standard is — roughly speaking — to be able to digitize any and all existing texts, after all.

But for actual new characters to be added they would first have to become popular enough to warrant inclusion. Neither Chinese nor Japanese is a language that produces new Chinese characters like they did historically. The barrier to get a character excepted beyond a fringe group is quite high — in any language — and there really is no strong need to create new characters.

1: Chinese, Japanese, Korean, Vietnamese (the latter two historically used Chinese characters as well)