The answer is hard to define and is more a question you should ask yourself depending on the game you're about to create.
Technically, everything would be ready for a neat 2D game, for 3D you can either go with HTML5 and a 3D engine, or start your way up with WebGL.
Nowadays the biggest problems are compatibility and performance. Your game might work well on your i7 CPU on a fast browser, but will be totally unplayable on a netbook with internet explorer. Also, Microsoft has a good history of promoting their own technologies, IE10 might not go the WebGL way in order to promote DirectX, especially since you can code apps for Windows with web languages. You need to define on what system you're planning your game to play on, if you focus on a particular system you can optimize towards it and use the technologies it supports. Keep also in mind that if the game is not stored locally you will need to take the bandwidth into account.
2D games are usually working smoothly on almost any system and can be used to create iOS simple games, with some limits of course. Depending on the game you don't necessarily need HTML5 Canvas and you could first try with plain old "DHTML".
So I'd say yes it is ready, but it greatly depends on your targets and if you are willing to spend a lot of time to optimize to the last bit every line and events of your code. And don't dream about simply putting your game online, thousands of users will not understand why their IE cannot run your game.