I refuse, point blank, to own more than one DSLR at any time. I started with a D70 and, via D200, D300 and D700, I've now got a D800. I use it occasionally. Personally, I doubt whether any digital camera, DSLR or rangefinder / 4/3rds or whatever will ever be deemed to be a "classic". I love using my D800 but I find what digital cameras produce is too clinical for my tastes.
Conversely, I have a Hasselblad XPan + 3 lenses, Hasselblad 500c/m and 500el/m + 3 lenses, Rolleiflex 2.8e, Nikon F, F2, F3HP, F5, F6, FE and FM3A, Exa IIa, Olympus Trip 35 and a number of other small point and shoots - and love using them all.
Occasionally, I'll trade one for something else. I've owned Leica's and Mamiyas, Edixa, Pentax and even Canons down the years. It's fun to play with these toys and, relatively speaking (other than the XPan) the gear is relatively cheap.
Digital will, I'm sure, continue to "evolve" but there's very little I can think of that would make me want to "upgrade" from my D800. 36MP and great low-light performance (for what I want) is plenty - at least for now. I (very briefly) considered the Df but £2,750 for a hobbled D4, packaged with an f1.8 lens didn't take me anywhere I want to go and there's no way I'd spend that much on any camera - all of what I buy these days is second-hand.