The old DA42 did 140kt IAS at 11GPH total flow rate - same as the TB20 but on cheaper fuel. I know; I was in it.
I would expect the new one to have a higher max speed but the same fuel flow at around 140kt.
Sadly the new engine will not have a known history for a few years. Anybody buying one now has to be feeling very lucky, but Diamond need a whole lot of people to be feeling very lucky otherwise they may go bust. No wonder they certified the DA42 with avgas engines, for the US market.
For a few years I have been hoping for a SE turboprop, unpressurised and not much bigger than a TB20. The nearest that ever appeared was the Grob 140 but that must now be dead, and it was way overpriced at (according to Grob) 1.4M euros. They were pitching it at the military training market. The huge cost of the engines and their poor SFC must mean that nobody will use them unless they can the FL250+ TAS gain, which in turn means pressurisation, and you end up with a big plane, and need a bigger engine to pull it along
