Xi never said Taiwan "will" be annexed by military force, and has expressed a lot of confidence in the prospect of resolving everything peacefully, just as the PRC has said for several decades now. Xi has merely said that military force will be used if necessary, which would evidently require circumstances that are not currently the case.

See here: https://www.theguardian.com/world/2019/jan/02/all-necessary-means-xi-jinping-reserves-right-to-use-force-against-taiwan

Obviously his comments are a little chopped up, but I don't think it's fundamentally inaccurate, it just looks scary to liberals because China Bad and they don't understand the situation at all. See the part about the "historical trend to peaceful reunification". He supports the traditional position of waiting as long as it takes if that can achieve their goal.

Edit: There are a lot of things to criticize about China and Xi and so on, and I think this site under-emphasizes that, but I feel compelled to mention that his stance here is completely the right one to take imo.