The SE isn't typically annual. They may release an iPhone every year but they are on their third iPhone SE? Or is it second? It's not the typical release cycle. Watch SE will probably follow suit I'd guess.
Whether it's worth it is purely subjective. I have an SE and in my opinion it's not, but if I decided I really wanted the ECG feature (for example) or really wanted the larger screen, then it would obviously be a good upgrade.