My $0.02:
I might consider spending $2500-3000 (by today's USD) but I can safely
say that I would not spend $5000-6000 on any DSLR, big sensor or not.
So a really high end, expensive Med format DSLR is of no use to me. What
I would like are the current D/DS features with a somewhat bigger sensor
and some better frmware (as discussed elsewhere, the exposure can be
flaky) and maybe a more waterproof body. To be honest, though, I'd be
just as happy with a slightly less flaky version of the DS and would
spend the extra money on lenses. This is just me, of course.