The increase in the group chat cap is likely to make it to the Google Play Store version of the app. But if you want to be able to chat right now with 256 people at once, you can click on the sourcelink and use APK Mirror to sideload the new beta build onto your Android phone.
WhatsApp is now completely free after it dropped the 99 cent annual fee. Besides messaging, you can make internet calls, send and receive video and voice messages and handle group chat. If you're offline and miss some messages, you will see them once you get back on the grid.
Facebook closed on its $21.8 billion purchase of WhatsApp back in October 2014, and the latter continues to add new features and update older ones. You might not need to be able to chat with 256 people at the same time, but it's nice to know that with the WhatsApp beta, you can.