Unfortunately for Sam fans it looks like his book is ending as well
Seems like they put Sam on the Avengers for two reason:
1. He’ll have a book when his movie comes out next year
2. JMS likely wants to keep Steve to himself the same way he wanted to keep Thor to himself. Putting Sam on the Avengers allows for Steve to be left solely to JMS, without events derailing his plans this time around.
Odds are long that JMS will stay on the book for long before bailing, if the WGA strike ends anytime soon I expect he’ll be exiting ASAP.