Except this group had lots of men in it.

I thought it was obvious - he saw the group of heavily armed angry women, that Tara found before, and knew they would be the key to kill off the Saviors.

I immediately thought of the settlement of women Tara came across a few episodes ago. The Saviors allegedly executed the men in their community, which would be a powerful reason to join anyone moving against Negan, and they have a huge stockpile of weapons. They've been living in isolation, though. As far as I know, Tara's the only one who knows they exist so if any recruiting was done, Tara was the only one who could have done it. Then again, someone's been wandering around in the woods that hasn't been identified yet. Some think it might be Carol (I don't), some think it might be Dwight (I don't), some think it might be a new character we haven't met yet (very possible) and some think it might be an old character that hasn't been seen in ages and was presumed dead (what I'm leaning towards). Whoever that person turns out to be, I believe
that's
who Rick saw at the end of the episode and he seems to recognize him/her in a good way.

It's a large group of wild women.
He knows that he'll die looking like this:
http://nerdreactor.com/wp-content/uploads/2013/04/Futurama-Amazon-Woman-In-The-Mood-Crushed-Pelvises.jpg

Tribe of Amazon female warriors (no pun intended) & Carol.

allies

I had thought that also. Carol wasn't out there just making blueberry jam every day, and where did she get that rifle?
They're gonna miss us when we're gone.

Alternatively Carrol secretly gathered an army

The only place such numbers could com from would be the Kingdome and that means its probably Darryl and/or the second in command guy who was eager to fight who brought everyone who was willing to fight even if the King wasnt.

Looked like he finally lost his mind. How could he get hoodwinked again, he probably thinks it is all over. He cannot be so confident as to think a group of people who he just stole from(you still lose) would help him fight.

Lori's ghost all Star Wars-like. Getting boinked by Shane's Star Wars ghost. Darth Vader in the background breathing heavy as he jacks to the whole scene.

EXACTLY !!! NUMBERS to fight the Saviors
An intellectual carrot , the mind boggles

I doubt he saw a familiar face. If anything, Rick smiled because he noticed their numbers (something he and his allies need if they want to beat the Saviors) and he's hoping to recruit them.

He saw no one