Why Andy was replaced
In case you haven't heard, Andy is being replaced by Sundar Pichai. No one has a clue of what we can expect... everything is just speculation. Here are my two cents.
Google and Android have always been at odds with each other. This may come as a surprise considering Google essentially built android. The friction comes from the old Battle between Native apps and Web apps, Cloud based and Client based, Thin client vs Fat client.
If you take a glance at Google's portfolio, you'll see that by and large, they are almost entirely a cloud/web based company. They host your Gmail on the cloud, they do searches on their servers, they make your browser and they might even deliver your internet if you live in Kansas. The one black sheep they have is, you guessed it, Android.
Chrome OS on the other hand, was built as a statement to how a modern Thin client should look like. Chrome OS made a few concessions to the pure thin client model, such as Native Client, Offline apps and local storage. But at the end of the day, you will almost always end up using some mix HTML5, JS and AJAX.
Android on the other hand does almost nothing to shift balance in the "Thin client" vs "Fat client" war. Most apps are coded in Java, they require to be fully downloaded before you can use them and they tend to be extremely platform dependent. These are fundamental problems inherent to the Fat client model.
People coped with these problems for 3 major reasons. One, the internet connection was slow and unreliable in too many parts of the world. Two, Web standards took too long to develop and were always behind what native apps had to offer. And Three, no one had proven that you could successfully consolidate the problems of the thin client into a commercially viable product, until Chrome OS.
Many tried and failed to make Thin clients in the past, Sun Microsystems lost to Microsoft Windows and Palm's WebOS lost to iOS and Android. Such is the price to pay for being too far ahead of your time. Sundar Pichai's success with Chrome OS was perhaps the greatest victory in Thin client history. One reason is that Chrome OS took part of the web offline, allowing you to access critical apps such as Google drive, Gmail and calendar without a connection. NaCl (Native Client) allowed companies to port legacy code to the thin client age, allowing for DRM in Netflix and RDP for windows. More importantly, Chrome gave access to experimental cutting edge features to curated apps using the Apps and Extension API's. Chrome OS has finally closed every technical hole in the thin client model, the only thing it needs now is help from developers. Android has lots of those, but more importantly, it has a large customer base.
But being large isn't enough. Windows, Mac OSX, iOS and Android are all dinosaurs of the technological Jurassic period, Google knows this. We can expect Sundar to take Chrome on Android to new heights. Web apps will become the norm, not the exception. Every new API, such as NFC, sensors and widgets, will be instantly available to web apps. The Chrome App store and the Google Play Store will be merged into one. Android will be Chromified, and Chrome OS will be given new web based steroids.