README: update news for next release

Change-Id: I5a8b65dd7008ddfa7d4aaf50d2330849455c8bd6
Reviewed-on: https://code-review.googlesource.com/26230
Reviewed-by: Jean de Klerk <deklerk@google.com>
diff --git a/README.md b/README.md
index 17d9d3e..769a731 100644
--- a/README.md
+++ b/README.md
@@ -33,9 +33,32 @@
 
 ## News
 
+_April 9, 2018_
+
+*v0.21.0*
+
+- bigquery:
+  - Add OpenCensus tracing.
+
+- firestore:
+  - **BREAKING CHANGE:** If a document does not exist, return a DocumentSnapshot
+    whose Exists method returns false. DocumentRef.Get and Transaction.Get
+    return the non-nil DocumentSnapshot in addition to a NotFound error.
+    **DocumentRef.GetAll and Transaction.GetAll return a non-nil
+    DocumentSnapshot instead of nil.**
+  - Add DocumentIterator.Stop. **Call Stop whenever you are done with a
+    DocumentIterator.**
+  - Added Query.Snapshots and DocumentRef.Snapshots, which provide realtime
+    notification of updates. See https://cloud.google.com/firestore/docs/query-data/listen.
+  - Canceling an RPC now always returns a grpc.Status with codes.Canceled.
+
+- spanner:
+  - Add `CommitTimestamp`, which supports inserting the commit timestamp of a
+    transaction into a column.
+
 _March 22, 2018_
 
-*v0.20.*
+*v0.20.0*
 
 - bigquery: Support SchemaUpdateOptions for load jobs.
 
@@ -44,7 +67,7 @@
   - cbt: Support union, intersection GCPolicy.
   - Retry admin RPCS.
   - Add trace spans to retries.
-  
+
 - datastore: Add OpenCensus tracing.
 
 - firestore:
@@ -56,7 +79,7 @@
 - spanner: Support Batch API.
 
 - storage: Add OpenCensus tracing.
-  
+
 
 _February 26, 2018_