Edit:
I wrote that kind of late last night after a long day shooting and a few beers, so I'm scrapping the whole reply and starting over. I would suggest you try to standardize your platform.
I shoot almost nothing but architecture and furniture. Here's the kit I take out to each shoot:
Arca Swiss M Line 2 View Camera
All about it here.Arca Swiss Rm3d Tech Camera
All about that here.Lenses (which can mount on either) 35mm, 43mm, 55mm, 70mm, 90mm, 135mm, 180mm
Phase One P65+
Canon 5d2
17mm TS-e, 24mm TS-e, 17-40 zoom, Leica R 28-70
Red One
RPZ 17-50mm, Cooke Panchro/i Primes (18,25,32,50,85,100) and a couple Zeiss ZF's 35, 85
THIS IS WAY TOO MUCH CRAP!!! But I use every bit of it.
I would love to use only the 5d2 and totally pimp it out, but I prefer working with the tech/view camera for composing stills and that little extra image quality. The Red is obviously for film work, which sadly the 5d2 isn't adequate for... moire problems are killer in architecture.
Which way should YOU go? Really depends on what you shoot. If it was only architecture, I'd tell you to ditch the Nikon and get a tech camera and a few lenses. You'd still have the Rollei for added flexibility.
For maximum flexibility/usability I'd almost favor selling everything and going Canon. Buy the full TS-e line and some fast primes for people/action work... 5d2 1ds3... your call. I say Canon, because even though I love my D3 way more than the 5d2... Nikon can't touch Canon's TS-e lineup.
You could drop down from MFDB to DSLR and none of your clients present or future would notice any difference in the imagery. I notice that difference and have just a couple clients who do so I stick with it... plus I just enjoy shooting with MF more (I find Tilt-Shifts annoying to work with --- even though my 17 continues to blow me away).
It's not uncommon for me to pull the Arca off the tripod and put on the Canon when I find it better suited and I've never seen a client react... during the shoot I'm talking about architecture in a way they would never expect someone outside the discipline to comprehend and I'm showing them images on the laptop that they love and by the end of it what's on the tripod has no impact on their experience.
Well, heh, except for the Red. That always blows everyone away... LoL.
CB