Boeing 737 successor Part V

I swear that this is the last piece in that series - before the Paris Air Show!
A recent piece in Flightglobal as well as a blog entry from Scott Hamilton this week shows that inside Boeing there are diverging blocks: one wants a new airplane, the other wants to reengine the B737NG and it seems like a "put them all in one boat"-solution to do it both. With a A320neo family arriving from 2015 onwards and a hypothetic new model from Boeing arriving in 2019 or 2020, with the CSeries entering the market in late 2013 and probably another 5 abreast aircraft from Embraer arriving at the end of the decade, who then needs a reengined B737NG? And if the backlog is so big that there are filled delivery positions even in 2018 today with todays B737NG, a reengined B737NG would only get a handful of orders from customers which did not get a delivery slot from Airbus, Bombardier or Embraer before the Boeing NSA is available.
So doing both makes no sense if the NSA is really slated for around 2020 - but a later arrival, around 2025 could make sense, as the differentiation against the A320neo in terms of engine and aircraft technology and thus operating costs could be larger then. That thinking should behind when Albaugh (quote Flightglobal) "questioned whether such an aircraft would be "good enough with rising fuel costs and emerging environmental regulations" and whether it could stay in service for 50 years." (quote end)
In the meantime, a reengining would make sense and would give that reengined B737NG a life expectation of at least ten years. At last years european ISTAT conference I spoke with some appraisers about the (the not yet launched) A320neo and they said that it would need a production run of at least ten years - the same should be true for a 737NGneo.
A "mild" reengining, maybe even avoiding changes to the front landing gear, should not bind too many engineering resources and should put Boeing in the position to counter Airbus if they should announce any changes to the A350-1000 that would make that aircraft to a better competitor to the B777-300ER than before.