I think Borza has as good a chance as anyone to test 1:40 under perfect conditions: he's got the right build (strength without bulk and a long stride) good pace judgement (very even splits) and a one-race mentality (which, as Trackhead rightly states, is the norm these days).
That said, I'm not one to believe that the next 800m world record holder will come from a distance background - while I accept that it's a *more* aerobic event than the 400m, I don't consider it an aerboic event in and of itself. Nor is it a pure sprint. It's unique.
Distance-orientated athletes simply won't possess the raw speed needed to open a sub 50 second first 400m. Pure sprinters won't have the basic strenght to follow up a sub 50 opener with a sub 50 closer.
This explains why the barrier is set to last for so long - the sprints and the distance events attract a host of athletes with the ability to switch in and out of specialities. (MJ in the 200/400, Geb in the 5/10)
The 800m requires isolation, which attracts few athletes and thus minimizes the chances for record breaking.
1:40 will be broken eventually - all barriers are - but it might not be when and where we expect it.
Martin