Also use the pyQgisVersion approach in QgsPluginRegistry

src/app/qgspluginregistry.cpp

@@ -253,6 +253,14 @@ bool QgsPluginRegistry::checkQgisVersion( const QString &minVersion, const QStri
   int qgisMinor = qgisVersionParts.at( 1 ).toInt();
   int qgisBugfix = qgisVersionParts.at( 2 ).toInt();
 
+  if ( qgisMinor == 99 )
+  {
+    // we want the API version, so for x.99 bump it up to the next major release: e.g. 2.99 to 3.0.0
+    qgisMajor ++;
+    qgisMinor = 0;
+    qgisBugfix = 0;
+  };
+
   // build XxYyZz strings with trailing zeroes if needed
   QString minVer = QStringLiteral( "%1%2%3" ).arg( minVerMajor, 2, 10, QChar( '0' ) )
                    .arg( minVerMinor, 2, 10, QChar( '0' ) )