If The Chilling Adventures of Sabrina were to make its premiere on The CW between Riverdale seasons 2 and 3, could the character make her debut towards the end of Riverdale season 2?
Now, The CW have announced that The Chilling Adventures of Sabrina is in development at the network, intended as a companion series to Riverdale.
Another point that strongly suggests Sabrina will appear in Riverdale season 2, is that The CW has done crossovers before.
Riverdale and The Chilling Adventures of Sabrina will exist in the same universe, and the options for crossovers are plentiful.