Having had some time to mull this over now, I hate losing Espinoza, but I don't think this is the end of the world. I like that we have Pomeranz through 2018; I wish he had more of a track record to go on, making this something of a gamble, but if his breakout this year is legit and he continues to pitch like a #1/2, this could turn out to be well worth it.
I love Espinoza's potential, and it will suck not to be able to follow his starts and dream on him from now on. Young pitchers with his upside don't come around every day, and I really pray we made the right choice here. Of course, he is also several years away at minimum, and a lot could happen between now and then. If we had to give up one of the top four, I'd have preferred to send someone like Devers plus other pieces, but it's done.
It's not a trade I'd have made, but given the uncertainty inherent with 18 year old pitching prospects and the fact that Pomeranz appears to be coming into his own just as he enters his prime, it's certainly not out of the realm of possibility that this does turn out for the best. We'll see.
(Side note: while there are valid arguments one can make for this trade, the fact that Pomeranz was an All-Star this year really isn't one of them. Brock Holt was an All-Star a year ago. Hopefully no one thinks we should trade Moncada for Bartolo Colon next.)