An Acknex Browser Plugin not, no. But JCL has already said that an acxnex plugin wont be realised. Already existing plugins (not sure what JCL had in mind) may be apparent on user's systems. It was already done using a java applet.

Years ago multimedia fusion had a very light plugin that downloads and runs its browser specific games on your screen (browser). many people downloaded it to play the games. Making your players install a plugin is not a matter of too much effort/creepyness of a plugin, it's how you advertise your games/products to the audience. If you do it well enough, they will install the plugin. Remember it's not about what you would do to play a game, but what your audience wants. You can't pull an audience of stubborn programmers over the edge that easy, but you can with gamers (of specific genres).