Some info about this issue:
According to Newsarama (and also a listing on the DC website for Batman #22), Josh Williamson (who writes The Flash) will be doing the script for Batman #22 instead of regular Bat-writer Tom King.
And Part 4 (in The Flash #22) will be out a week later (May 17th instead of May 10th).DC's current crossover "The Button" will undergo a few minor changes in plans as it moves towards its May finale.
First, The Flash writer Josh Williamson will now also script Batman #22 rather than regular Batman writer Tom King - a decision with several reasons behind it.
"As we worked out the story details of the issues together, it become clear to me that Josh could script Batman #22 better than I could," King explained. "My responsibility is to put out the best Batman issue possible for the fans, and in this case, the way to do that was to step back a bit and let Josh take the lead. Reading it over now, it's obvious I was right; I love the issue and I love this event, and I can't wait for everyone to get it in their hands."
Williamson added that scheduling considerations also played a part in the decision, saying "Tom and I had been working together on this insane 'Button' crossover for months, so when he needed to focus on the next arc of Batman with 'The Brave and The Mold' and 'The War of Jokes and Riddles,' it was super easy for me to jump in and help take the script across the finish line. Tom and I had talked with DC editorial about what we could reveal in Batman #22 and how it would play out and we’re happy with the story we developed together. The next parts of the crossover are going to be a wild ride."