I lived with a 2.3L turbo 5 speed T-bird for many years. '83-'02. I'm sure that was a world apart from modern turbo engines but I would not want the 50 to go with a turbo engine. I re-built it, balanced, blueprinted, ported, polished, water cooled the turbo... I only chose it because of the sporty style, seats, gauges, suspension, air dam and on paper had close to the same HP. In my day replacing turbos was replacing tires, normal wear and tear.
I really like the 3.7 but it is often criticized, that it "lacks the refinement of the V6s in some competitive models", and is less fuel efficient. I guess it is getting a little old but it's earned high praise for years. It's practically legendary for its high performance and reliability. So I see impulse to update the power plant but if they go with the 2.0 it better come at a much lower price point.
It looks like the old 3.7 is out. If the only option is a turbo I might just want to keep my 40 in two years.