Most Upgradable MB, 1st time DIY'er needs help!!!

I am diving into my first DIY PC build.

What I want to know is that, if I want to have the most "upgradability" for as far into the future as possible is the Motherboard the key component to invest in?

And if so what is the most flexible/capable/upgradable one out there? And is there something new about to come out on the horizon that is drastically changing the architecture/environment/capabilities, etc.

Hopefully my question is clear. I am still not quite sure all the questions I should be asking. I know what my goals are. Just not sure what components to start with. I am assuming the Motherboard is where to start.