Interesting side note: Steve Augeri, the first singer after Perry, sounded much like Perry. Towards the end, when he developed his throat condition, he was lip-synching live, and they were piping in vocals recorded from before his throat condition.
Jeff Scott Soto, who has a very powerful voice, just didn't sound enough like Perry. He also couldn't quite get to the top of the range for some of the classic songs. But sounded good on the more full-voice songs.
You might not know his name, but he sang with Yngvwie Malmsteen, and also was Marky Mark Wahlberg's "singing" voice in the movie Rock Star.
Current singer Arnel Pineda is the closest I've heard to Perry. He can really hit all the notes.
I think that nobody really knows what kind of vocal chops Steve Perry has left. He doesn't sing for anyone, and hasn't in years, other than occasionally in the studio. One would think, however, that a singer's voice at age 60 would not be able to go to the same places as it did at age 30.
That said, nobody would care if he and Journey reunited. He'd still sound like Steve Perry, and like all singers his age, they'd just play some of the higher songs in a lower key, and he could duck some of the highest notes live, like he did even in his prime.
Nobody hits every note, every night, for a whole tour.