It won't go supernova anytime soon. They detected neutrinos from near that part, but not exactly Betelgeuse. And from my understanding the neutrinos are detected a couple of hours before the star goes supernova. This was days ago. It's just people getting exited for the no chance possibility.
http://www.astronomerstelegram.org/?read=13410Its been dimming for more then a month, and further observations show even more. And suggests a 9-10% radius change, along with the temperature of the star changing by 100 K. These changes are drastic for a star where changes are static over millions of years.
Changes for such a star is normal and continuous. They get bigger, in terms of volume (not mass) and then get smaller.