iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Apple Limits Access to iWork for iCloud Following 'Overwhelming Response' to Public Beta
We've had an overwhelming response to Numbers for iCloud beta. Please check back soon.
In the meantime, you can continue to store your spreadsheets in iCloud.
iWork for iCloud is a browser-based implementation of Apple's iWork suite of productivity apps: Pages, Numbers, and Keynote. The service will work with Safari, Chrome and Internet Explorer, offering a native-like experience on machines and platforms that do not or can not have the full iWork apps installed.