I don't know what you mean by plugin? For your phone?
If we are talking Flash: Flash is a two part solution. The software developers use to make the content and the plugin used to broadcast that content on various browsers. This news essentially means that flash will no longer fight to have their plugins included on a lot of mobile devices. But they have been losing that fight anyway, so I don't see that anything has really changed, other than they can now focus on battles they have a batter chance of winning. But I seriously doubt this will kill flash. People have been saying flash will be dead for years now. It's still going. Why? Because the software developers use to make the content is unmatched by anything out there. And even if there was a comparable solution, it is going to take years upon years for existing flash content to disappear from the web. I have always maintained that it would be in these mobile companies best interest to find ways to display this content. Until then, they will never be the ideal platform for browsing the web.
HTML 5 competes against the plugin as a way to publish content. I personally believe Adobe will soon find an effective way for developers to continue using their flash software but rather than publish that content as an swf file, it will generate the HTML5 code. (This already exists, but needs a lot of fine tuning)
The only issues I have with Using HTML5 over flash's plugin is A: HTML5 cannot do some of the things that the flash plugin can do, and B: When you publish something to HTML5, that code is out their in the open. Anyone can steal the code I might have developed and use it on their site. Time will tell, there may be solutions to those issues in the near future.