Thank you for the video guys. Your enthusiasm and love of photography puts a smile on my face!
Jonathan, I'm in a similar space.
I had a 1DSmkII and a 1DmkIII with a nice collection of lenses for shooting mostly wildlife and landscapes: 16-35, 24-105, 70-200 f4, 100-400 and 50 f1.4. And a Pentax MX-1 which is my "friends and family" camera :-)
I finally took a deep breath and sold the 1Ds and the 24-105 in order to finance a G6 with the 14-140, 100-300 and the 45mm macro. Here is the thing: for "friends and family" stuff, the G6 plus 14-140 is absolutely fine as far as I am concerned. And if you're into macro, the G6 plus 45mm is also perfectly fine, especially if you think how much weight you are saving! I'm getting to a certain age, where this matters a lot.
But it's not all wine and roses. The future is most definitely mirror-less, but the present is more of a mixed bag.
BIF photography with the G6 is really challenging. And it's not just the tracking AF (I used to manual focus in the old days, so adjusting my shooting style again is not going to kill me), but also the EVF black-out and the EVF and shutter lag. Of course these things will get sorted out in the next 5-7 years (faster CPUs, etc), but in the here and now, if a new birder/photographer asked me whether they should spend over £1,000 on a high end m43, I would have to advise them that they can save money and frustration by getting a second hand DSLR and a good lens.
And while we're on this thorny subject, the prices for quality m43 lenses is, I'm sorry to say, ludicrous in the UK. Why would I choose a Panasonic 35-100 at nearly £900, over a Canon 70-200 at £800?
I certainly hope that Sony, Panasonic, et al keep pushing the big boys in terms of performance and price. For now, I'm selling the Panasonic 100-300 and I'm pairing the G6 with the Canon 16-35 when I want to do landscapes (I know the combo sounds/looks ridiculous but it does work very nicely and my back is very grateful indeed).