Having worked at Boeing, it's strange to imagine such an acquisition. Boeing is the polar opposite of a software startup, and ForeFlight's about-page shows them to be founded by software entrepreneurs. I will be impressed if they can make this work. What does Boeing hope to get from this that they couldn't get from them as a partner or supplier?
Boeing gets to integrate Foreflight into their Jeppesen product line. Jeppesen’s FliteDeck Pro is the product all of the heavily regulated operators like airlines are using in the US. The current iteration of FliteDeck Pro from Jeppesen is kind of a disaster. On a last gen iPad Pro their map page frequently chokes if you turn on too many layers. It also constantly has a weird bug where it gets locked on the airport moving map animation and can’t get out to other charts. Many in the airline industry are excited for the next release of FliteDeck Pro as it will use Foreflight under the hood, hopefully fixing many of these issues.
Boeing owns Jeppesen, which specialises in flight planning and related software, so it's a very natural strategic acquisition. And there's no shortage of potential projects where Boeing could use the support of a team that's really good at aviation UX too...
Boeing and Airbus both have their own incubators for small startups so it's not like they're totally averse to the SV mindset when it doesn't conflict with their regulatory and safety processes.
Boeing is a lot more high tech than people give them credit for. In my opinion, Boeing could only serve to benefit ForeFlight as now the company has significant backing as well as deeper access into cutting edge flight systems tech.