It would be nice, sure. The issue with having an upgrade system in place for the old raid weapons and armor would defeat the purpose of earning new armor and weapons to challenge the new raid, or of even doing the new raid if you already were able to get the new max level using your old armor. I can definitely see an upgrade coming to the VoG itself that would increase the armor and weapons received from it to the higher level cap. Just after Crota's end has been out for a while. This keeps old content relevant and doesn't defeat the purpose of doing the new raid.