The Simpsons need to age

I don't think this idea will shock anyone, but after watching the latest episode of The Simpsons tonight I again concluded it needs to be refreshed.
The only way the writers can do this, in my view, is to let Bart, Lisa and Maggie age by a year.
I know, I know, South Park did that at one point but they also did an episode called Simpsons Already Did It so stealing from other animated shows is not new.
Heck, South Park, Family Guy and American Dad are all crude rip-offs of the Simpsons anyway.
By letting the characters age it can put them into new situations, new regular characters can be introduced and new ideas tried.
We had a glimpse in an episode where Lisa was promoted to 3rd grade and Bart demoted but they didn't go far enough.
What would happen if Bart made it to fifth grade (he could go on an episode of Are You Smarter Than A 5th Grader), how would Lisa cope with third grade, Maggie might finally get to speak a bit. The possibilities are endless.
Something needs to be done to bring The Simpsons back to its former glory. Season 12 is about to be released on DVD and by this stage the show was less consistent and memorable episodes fewer and far between. The classic Pinchy episode is now over 10 years old and I don't think there has been an episode since anywhere near as funny.
So, challenge extended writers. Over to you....