for me, it's just F4.
While Aaron's Thor sounds like a really good premise after finding a lot of Esad's Thor art online today, I changed my mind. Esad's art does look like it would fit what Jason is doing, it's just not my taste and for a $3.99 book, there's no way I'd splurge for that.
If Defenders goes bye-bye (please no... :( ), then I might take a peek at Hickman's Avengers or New Avengers depending on the characters involved.
While I can get discounts pre-ordering $3.99 hard copies, if I'm not in love with a current title, I buy digital only so it's a bigger hit on my wallet. F4 will make 2 $3.99 books and I'm realizing I have to put that money elsewhere.