(Disclosure: I'm a PM on the Flutter team.)
Obviously I don't know how you've structured responsibilities internally, but what I've seen before is, that the quality of individual components, or plugins if you will, live and die by the interest of the teams and people behind them.
Qt has this very same problem, often leading to some bugs ageing unacceptably long, or features never properly maturing, simply because there's little to no inside interest. NPM has a variant of the same problem as well. I'd venture a guess that a large percentage of packages on NPM right now, is downright abandonware.
I will be keeping a interested eye out for the developments of Flutter and I'm hopeful you succeed in this space. There's definitely room for it.
With regards to the native stuff, I'm mainly coming from a performance perspective on GPGPU and computer vision applications. I think going forward, there's going to be a huge increase in AR/MR apps, that will need easy access to do heavy lifting on metal. Coincidentally, I was lucky enough to catch a quick chat with Michael Thomsen, after his talk at Coldfront recently and he mentioned that, that was indeed on the roadmap. If you guys manage to provide the easiest cross platform way to do Vulkan/Metal or whatever the next-gen iOS and Android HAL is going to be, you're definitely going to come out on top.
Also not having a JSX like syntax. I went into RN expecting to hate JSX, but I ended up loving it.
Doing UI development with nested {} is so hideous in comparison. I am impressed at the quality of UIs Flutter can make, but the code behind them is, IMHO, much harder to read than the RN equivalent.