Depends on your uses. If you strictly are using the team for arena and don't plan of getting the team to elite insane territories because you're trying to get top 10 with an old team, then you don't necessarily need to take 3PO to G13. But considering LS Geo TB and the speed boosts he gets, then yeah it's worth bringing him up.
I think you can probably stop at G13 though, relics might be a bit overkill since the only thing he really gains is survivability and he's already pretty stout by the time you get to G13