Toyota, Honda, and Nissan use ten year cyles for midsize platforms.The 2007 Toyota Camry is just a Major Revamp of the 2006 Camry. Just like how the 1997 & 1987 Camry were revamped compared to their 1986 & 1996 predecessors.
This is conjecture!
The Epsilon Malibu(The standard of Epsilon)
2003-All-New
2006-Mild Restyle
2008-Major Revamp
2011-Mild Restyle
2013-All-new on Epsilon 2
The Epsilon G6
2005-All-New
2009-Major Revamp
2012-Mild Restyle
2014-All-New on E2
The Epsilon Aura
2007-All-New
2010-Major Revamp
2015-All-New on E2
The Epsilon LaCrosse/Allure
2009-All-new on E1 Revamp with Pontiac G6
2012-Mild Restyle
2014-All-New on E2
The Epsilon Cadillac BTS
2010-All-new on E1 Revamp with Saturn Aura
2013-Mild Restyle
2015-All-New on E2
From 2013 on, GM will promote a midsize platform cycle of ten years. The lifespan of a midsize platform would be 12 years but, no product will be on it more than 10 years. Midsize cars will premiere in a particular order.
Chevrolet-Cheapest product sets basic standards
Pontiac/Buick-Improved for Midlevel standards
Saturn/Cadillac-Improved further for Luxury standards
This makes the most sense to me, I know its not based on actually GM Spreadsheets but, it does sound relatively inexpensive compared to lauching a new midsize platform every 5 years for each brand. The Camry is still essentially the same unnder newer steemetal. The only real diffrence is the new engines & transmissions. GM should copy or modify this idea. Dramatically restyle & Improve the Engines & Transmission for a major revamp of an existing platform.
By 2008, GM should give all its ecotecs VVT & give all its HF V-6s Dual VVT & Direct Injection. With the E1 revamps GM should give all Epsilons hybrid versions. When Epsilon 2 really does come out. The engines will likely not need hybrids since they will have Continously Variable Displacement. CVD combined with functional CVTs would improve E85 engines MPG figure by at least 50% over non-CVD engines. All without eco-damaging Lithium Batteries that are tooo costly even by 5-6 years from now. Hybrids are just a temp solution until more advanced technologies replace it.
This is just a guess but, when E3 comes out in 2023. I'd expect Camless Engines to be in them. assuming the market isn't revolutionized by hydrogen.
1900s-LHV engines premiered in mass production.
1940s-OHV engines premiered
1980s-OHC engines premiered
2020s-OHA engines premiered(Overhead Actuator)
Ok, I'm having a little too much fun now. I think I'll call it a day now.