One thing that became quite apparent is that sales will be concentrated on a fewer platforms. So, for example, I'm not expecting Sony developing another traditional handheld platforms, and therefore focusing on its home platform. In early 2000s, the market was basically one home - one handheld; the other systems were just noise and were not relevant at all.
While we're pretty close already, in the mid-term, I suspect we will pretty much end up with a three platform market.
Platform 1: iOS/Android - Effectively the same platform for most intents and purposes. This is the biggest platform, though as it's not optimized to how traditional gaming is defined, it's hard to cover every genre and interest that currently exists.
Platform 2: Nintendo Handheld - Whether by continued minor relevance or a NintendOS setup, I suspect their home console will continue to not really be a part of the picture, leaving us with this as the dominating dedicated device.
Platform 3: Sony Console - While I think there's a lot of room to move downward here in terms of relevance, especially if we take the obvious route and they don't make a follow-up to the Vita, the support Sony has garnered largely appears on two or more of their platforms, in many ways making their various devices one platform. The platform that Sony will definitely continue to make is PlayStation home consoles, and due to their success in the West, any Western targeted Japanese titles will likely appear there. As such, I view (Sony last-gen system)/(Sony current-gen system) remaining as at least a smallish enthusiast platform in the mid-term.
I don't think any other venues really receive the kind of support required to be notable market factors.