Daniel, the Rollie kit you describe would be an excellent setup - if medium format actually fits your shooting style and most-frequent subject matter. Rather than relying on the marketing blather of digital zealots, you might be better off actually assessing your imaging needs. That might point you to MF or even LF.

I'd agree with Bob Fowler, though. If you can afford to keep the D70 for what it's good for (and, it's a pretty good digital), do so. You'd only get a fraction of what you paid for it, anyway.