I do think that weight / size is a factor. My camera and lenses weigh about 2.9kgs and then there's extra batteries, a flash, filters etc so I guess in the region of 3-4 kgs when in the rucksack. Altogether it's quite a lot to lug around so I've taken to leaving most stuff at home and taking the bare minimum with me.
But that makes me think what's the point in buying all this kit and just leaving it at home ? Surely there's merit in having less bulk ?
I'm also tempted by the IQ that I see from the likes of the e-m* range. Whilst my d7000 can produce some lovely images, it can also miss the subject ( probably my fault for shooting at shallow DoF ? ) and I see new technology as having leapt forward since the d7000 came out.
Ultimately, change is down to money. If I sold everything, I might get £1000. Which doesn't buy me an e-m1 + 12-40