I'll echo what my leaguemate said about the arena. When you promote, you get a significant boost to attendance through interconference play, and you definitely want to have an arena sized to take advantage of that.
I haven't looked too in depth at your team, but I would say that with your roster as it is composed now, with no changes at all except another year, you'd likely struggle in III. Not knowing the skills of your players exactly of course makes that a much rougher estimate than I'd like, but that's just my best guess. Still, with an enhanced arena and maybe a couple of intelligent purchases once you've been in your new league a few weeks and know what to address, things may be entirely different. You may end up with two teams tanking in your conference, for instance.