If you want to buy a NEW machine for fast IFR touring, then don't bother buying anything buring Avgas now....wait until you can get a decent jet burner and rent / beg / borrow /steal in the meantime.
Yes, but WHY??
Why not avgas? What is the disadvantage of a TB20, Cirrus Mooney? What is the fast long distance IFR pilot waiting for? Is there any evidence that diesel will take off in the next 5 to 10 years? Sure, if you plan to fly in Africa or the third world then lack of avgas is a problem, but most tourers they will not leave the western world! You might as well go for a mogas burner and travel very light, though availability of fuel is still a problem. At least you can run your rotax on avgas if necessary.