What kinds of products are missing in 2019 and are going to get a lot bigger? (Not limited to infrastructure)
I recently picked up an iPad Pro (2018 model). Before owning one, I thought of it as "just another iOS device." I've owned other iPad models in the past. But this iPad Pro in particular is different: it represents a huge opportunity to shift day to day workloads to it. It's so much closer to just being a computer in the... useful sense.
I think iPad Pro-focused software will grow. I don't necessarily think that 2019 will be huge for it, but I think a lot more people will pick up on this trend.
What do you credit for the success of your open source projects like Vagrant?
A lot of things. A lot of people!
I think the early adopters that help shape the products, take the risk in using an unstable product, etc. are a huge part of that success.
What other open source projects are you a fan of?
Besides the big obvious ones like Vim (I'm a vim user)...
I've really loved watching the serverless stuff take off. I think a lot of it has major issues still but its definitely a radical way of thinking and I give a lot of credit to the "crazies" trying to make it a real thing (I'm not saying it won't be).
What steps would you recommend to an early-career developer to position themselves to work on successful large-scale, well-designed software projects?
I explain in other answers, but be more than just a good coder: be good at communication, be kind, be pragmatic, etc. From there, work on some products and continually shift towards what you want to do.