87 & 71 are guarantees.
68 basically comes down to when/if Jagr wants it, like it or not. Anyone else wearing 68 for the Penguins would be a travesty, so just make it official. I hardly have warm fuzzies for Jagr, but even if his career extended long beyond Pittsburgh, he'll be remembered as a Penguin.
58 is more plausible than a lot of people want to think, but is far from a sure-thing.
Pretty much everything else has been assigned elsewhere. That doesn't mean a number can't be retired...but Briere's number was uncirculated for 3 decades before officially being retired. Enough randos have worn 10 that I feel safe saying Francis just didn't spend enough time with the Pens to get that honor. If 10 didn't, 77 certainly didn't. Beyond that I don't see any serious contenders. Considering the 2 numbers the Penguins have retired right now it's hard to image we suddenly start retiring guys from 30 years ago now. As long as Mario owns the team I wouldn't expect us to throw number retirements out like the Canucks do.