Don't Wait if You Find Something You Like
If you're shopping and you see something that you like, whether that is one of the current Apple Watch models or an alternative like the new Moto 360, Ticwatch Pro or another wearable once you find something you like, it's a good idea to go for it.
If you find a good deal and get an upgrade from nothing or from a very old model, it makes more sense to get the upgrade you want right now and enjoy it for the next year.
You can always sell an Apple Watch for a decent amount on the used market to pay for part of your upgrade later on. This is a good reason not to wait for the Apple Watch 6, especially this far out.