The rant between DSLRs and mirrorless cameras has been going on since the inception of first mirrorless interchangeable lens camera. It all started back in 2004 when Epson, yes Epson, brought out the very first mirrorless camera. It wasn't marketed as a mirrorless camera back then and to be precise it was a rangefinder but it sure had the sensor right in front of the lens.
Subsequently, several mirrorless cameras started rolling out one after the other from renowned brands including Leica, Olympus, Fujifilm, Pentax, and Panasonic. By 2008 Mirrorless cameras were considered as a lifestyle product given their beautiful design and look. The picture quality they boasted was way better than any point and shoot camera could ever even imagine offering. This was also the time when especially the Indian camera market was flooding with compact point and shoots.
In 2010 Sony came into the picture bringing out mirrorless interchangeable lens cameras in their complete form. Sony's NEX-3 and NEX-5 MICLs were very rudimentary back then and no one ever even questioned whether MICLs could replace DSLRs in the future.
Parallel to this, DSLRs had found a great market to provide for and in 2010 Canon EOS 5D Mark II was the talk of the town. Canon's 7D had also created a fan following for itself. Endless line up from Nikon and Canon had started finding consumers in India.
MICLs had however grabbed attention for their compact size and the lens changing capabilities. This is perhaps, where Sony found an opportunity to place itself in competition with DSLRs.
In 2012 Sony's Alpha 7 r dropped in and the debate between MICL and DSLR supporters started heating up. Alpha 7 r was a great camera but it had few serious issues. The electronic view finder was laggy in low light conditions along with a body that was not meant for serious outdoor and wildlife photographers. Alpha 7 r was water resistant yet it did not have the solid built of DSLRs. However, the camera did surprise professionals with its stunning video recording abilities. It was also the first full frame mirrorless camera.
In 2012 it was impossible for Sony's mirrorless cameras to overtake DSLRs but those who knew cameras well were preparing themselves for a better mirrorless camera which would debut soon and it obviously did.
Between 2013 and 2015 Sony launched a series of high-end mirrorless camera. Alpha 7S, 7SII, and Alpha 7RII came in with an improved viewfinder and unmatched image quality and video recording capabilities. Mirrorless cameras for the first time had outdone DSLRs and Sony had shaken the roots of DSLR manufacturers.
Mirrorless cameras have been adopted by several professional photographers since then. The diversity of colors offered by Sony's high-end MICLs is unmatched in quality. The popularity and reliability of MICLs have motivated imaging giants Canon and Nikon to tread on the same path as Sony. Nikon recently made it official that it is working on a mirrorless camera. Canon was a bit early in adapting to change and already has EOS M series with mid-range MICLs.
Now that, mirrorless cameras have taken over DSLRs in quality are we going to see a transition in user base? Well, I still think DSLRs will last another decade. Sony's best mirrorless cameras fall in the range of Rs. 1,70,000 to Rs. 2,10,000. While high-end DSLRs are nothing cheaper, there are still cameras in sub 100k segment that have a matching quality to MICLs in the same price range.
Moreover, wildlife photographers and outdoor enthusiasts will not switch to MICLs unless they are encased in a rugged body. Let's get real DSLRs can handle any amount of abuse ranging from heating to freezing and insane shocks. Yes, they are heavy and require heavy backpacks to carry along but there is no alternative to their built quality. While photographers have moved on to MICLs they still rely on DSLRs in the toughest conditions.
Sony is on the verge of bringing a big change but now is also the time it needs to push hardest. MICLs need an insanely lasting body and without it, DSLRs are as good as MICLs.