I can't estimate the range of a trijet without a good look. Thing is open rotors are heavy too, as is the structure keeping them in place. Then noise is a problem, fibrations, hot gears, lubrication. They didn't stop for no reason in the late eighties..
Still : a fuel consumption reduction of >20% make OEMS look again (Snecma, RR).
I observe that Pratt and Whitney want to make a geared turbofan with 203 cm fan diametre. Producing 30 000 pounds thrust.
No doubt they are aiming for a 20-30 klbs familiy for the next generation NB. The 757 with it srelatively big fans is very high on its wheels. I think most studies from Boeing and Europe move the engines up the aft fuselage for that reason.
Last year I did a study on this with Henry lam, assuming GTF on a five abreast 110-165 seater.
http://www.airliners.net/discussions.../3513052/1/#40