In 2010 I sketched a more radical 737 upgrade, with lenghtened gears, a 787 style cockpit for fun.
Could Boeing Do A More Radical 737 Upgrade? — Tech Ops Forum | Airliners.net
Boeing doubted not for months but for yrs. If they had taken a decision in 2008, when Airbus was already mulling a re-engining. (warned them in 2006:
Proposing the A320 enhanced performance — Civil Aviation Forum | Airliners.net )
However the reality of the 787 developments together with 747-8 problems, plus the blind faith the 737 would be just fine, pushed Boeing into a position where John Leahy (Airbus) kind of launched the MAX..