On the same panel at SMX Munich (mentioned above), Zineb said that this 4/21 change will be bigger than the Panda and Penguin updates. Again, we think this fits well with an infrastructure change. It is unclear if all mobile devices will be impacted in the change or not. The change might be more impactful for Android devices or might impact Android and iOS devices equally—though currently we are seeing significant differences between iOS and Android for some types of search results, with more significant changes happening on Android than on iOS.
Deep linking is a key distinction between mobile SERPs on the Android OS and SERPs on iOS (currently, SERPs only display Android app deep links, and only on Android devices). But there is reason to believe this gap will be closing. For example, in his recent Moz post and in his presentation at SMX West, Justin Briggs mentioned that a few sample iOS deep links were validating in Google’s deep link tool. This may indicate that iOS apps with deep links will be easier to surface in the new framework, but it is still possible that won’t make it into the 4/21 update. It is also unclear whether or not Google will maintain its stance on tablets being more like desktop experiences than they are like mobile devices, and what exactly Google is considering “mobile.” What we can say here, though, is that Android tablets DO appear to be including the App Pack results, so we think they will change their stance here, and start to classify tablets as mobile on 4/21.
Emails are also increasingly impacting SERPs—particularly mobile SERPs), since mobile email opens have grown by 180% in three years, and Google is trying to take advantage of this increased engagement on mobile devices. As of now, schema can be included in emails to drive notifications in the Google Now app, and also to let Google surface marked-up emails in a browser-based search. This all happens by virtue of Google crawling all emails that come into your Gmail account, and indexing them to your user-profile so that they are accessible and able to rank like this across all of your devices (even if you aren’t currently logged into your Gmail account on your phone). Optimizing emails for mobile search is also becoming more important, and in the 4/21 update Google could do more to push the use of Schema markup in emails to drive personalized search results like the one shown to the right.
Inclusions like this mean that even if you are able to maintain your keyword rankings in mobile search after April 21, you may not necessarily be able to sustain your mobile traffic.