If a happy ending is all you wish for. Shounen will be shounen I suppose.
I personally don't want to see the same old script with the atmospheric battle in the end, and than, voila, happy end, fin. Sure, its not that bad sometimes, but only sometimes.
Yes, shounen will be shounen. What else could it be? The statement is like saying that anime is anime. Shounen is in the end just one genre of anime, nothing more, nothing less.
The atmospheric end battle is used is sooo many anime, not just shounen, but any kind of. Even that kind of ending can be messed up totally; for example, Claymore which has the shittiest ending in a series I have ever seen and it only had 26 episodes.
The truth is, most people do like a happy ending, they want to see a dramatic final battle before the story ends. Not just in those forever lasting shounen series, but in short ones as well. What kind of ending each anime has, depends
totally on the story writer, the length of a series has absolutely nothing to do with it. It raises the probability of having such ending, but it never forbids any other kind of ending.
How many anime do you know, any length of series, that have a sad ending? Happy endings are part of the story, it sells. Not only in anime but also in movies and TV series.
It is true that the shounen series could change their scripts little bit more, as they really seem to follow the same script in each series. The sad truth is, they are not trying to make it something special, they are making it something that sells. There has to be a reason why series like Naruto, Bleach and Dragonball are so popular. Some shorter anime series with better story etc. which are not even near as popular as those. They are not making the anime for their own satisfaction, but for profit like everything else.