sadly I think no more players are deserving of retired numbers. you DO NOT retire numbers just because you want to, ask the Montreal Canadians who have just about every number from 1-20 retired, and every current player is forced to have some crazy number.
Lindros and Leclair were great, and Hextall was a huge part of this team and its image, but none of them brought the cup to Philly, so none of them really deserve their number to be permanently retired in this city.
Mark Howe got retired because he is in the Hall of Fame and was a great player, but you gotta believe his last name has a lot to do with it. You wont see Eric Desjardins' name up in the rafters, even though he was a very similar player to Howe and was the backbone of this team's defense and leadership for 11 seasons.
I think the next number to be retired... might be 28, 10, or 14, and on a wildcard/longshot I'll say 26. We'll know somewhere around the year 2035 lol