i'll paste together my thoughts since the second half got lost under most of the comments. this is from the article posted earlier today.

[quote]this would be totally awesome if they did a university arc and showed their dreams of being musicians destroyed as they drift further and further apart and deeper into adulthood to show that life after their little high school tea party sucks and no amount of optimism can change shit.

Mio will start to resent ritsu and yui because she had to lower her university standards so that they can all go to the same school as they start to realize that they will never make it in the music business and that they need a real education to fit into the status quo. mean while ritsu will conintue to chase an impossible dream only to find out that yui is not at all serious about starting a successful band and is only interested in reliving their carefree days in high school never to grow up. mugi will dissappear as she is force to inherit her family's empire of chain stores for musical instruments and she will come to hate music because it is her fame and wealth from selling instruments that has torn her apart from her only true friends in the world.

azunyan, ui, and jun will try in vain to keep hokago teatime alive but will fail. ui and jun will continue with high school life but azunyan will always be the odd man out so to speak. after spending her first 2 years hanging out with one grade above her, she will find that she cant quite "click" with her peers and will spiral into a depression of loneliness. she will start to blame herself for letting the light music club disband. however, it wont all be bad. azunyan will be the only one to get out of this a better person. she will learn to accept her failure to continue the light music club through the support of the only friends that she has left, ui and jun as well as her new teacher, sawako sensei.

through this bitter experience she will grow up to be a stronger person who will always cherish her time with the once carefree hokago teatime. but there comes a time where one must realize reality. good thing for azunyan its not too late. there will be a tearful graduation as the original 4 members get over their differences and forget for one day that life hasnt worked out the way they wanted and come together to celebrate their beloved kouhai's graduation. they may not have been the best sempai's but damn it they tried their best! manly tears will be had as this will be the close of that which will be known as k-on.

azunyan's story will be a seperate spinoff.[/quote]
K-on had a lot of tear jerk potential if they pushed the "growing up" angle more.