Since its Windows on every device type, although they haven’t mentioned anything in the build specific to mobile, it is and will help mobile a lot. This build is aimed at “needing windows to loving windows” for devs, designers. The more people use windows, the more userbase the devs can target and make apps for. They are trying to solve the chicken and egg problem now.
1. It just gave a solid reason for designers and developers (who preferred OS X, linux mint) to switch to windows. The pen features that MS is bringing and bash will make u want to work in window’s design tools (adobe tools etc) than mac. This is want apple did way back.. (More users)
2. Legacy apps can now be converted to win10/UWP apps with the App converter tools they introduced, so we u will at least some % try to update their apps to leverage the new APIs and Windows store. (More apps)
3. Now with Caas (Conversations as a service) and Bot framework, they are making devs build bots for their apps/services and since this feature is only available in the Windows ecosystem (outlook, skype, etc) they are giving great reason to switch to their services. And all these bot services and cortana would be so much more powerful if u were using their services. Like if u use outlook, it helps cortana be an awesome assistant (just like Google now) in any bot in any app because it knows ur meetings, knows your friends (demoed at build). And once u are in a Google/MS ecosystem wouldn’t you consider giving their ecosystem a try? try their surface tabs/phones? (More adoption)
So as the adoption rate increases this year for windows 10, so will apps. I see a lot of new apps, services that I use everyday come as win 10 apps. From what I hear they wont be releasing a new surface tab this year but in early 2017 (18 months instead of a 12 month cycle), I believe this is because they want to finish their surface phone as well. One of MS executives was mentioning that if they came up with a new phone it has to be revolutionary like the surface book (new category) and they are stopping the lumia line this year (rumors). Lumia 950 review.
If the new surface phones can run x86 apps or some other revolutionary idea, windows 10 would be ready with apps coming from legacy apps, compatible apps for continuum, hololens, iot and from a lot of other sources.