In the first Kingdom Hearts game, Leon said that he won't use his "real name" until this world (Hallow Bastion) was restored. Does that mean, since the events of KH2 brought back Radiant Gardens, that we will be able to refer to him as Squall again in Kingdom Hearts III?

I doubt it.

I don't think so. Besides I'm still going to call him Leon because I like that name better.

We should call him Mr. Leonhart.

Nah.He was trolling.

I doubt it.

This. I will always call him Leon in KH (unless he actually does change his name) and Squall in FFVIII.

Just saying because if you talk to him in Hallow Bastion, he says he'll start using it again, so who knows.

Squall LEONheart

In Kingdom Hearts Leon will always be Leon

I don't think Leon will be called Squall, or at least not that often.  Yuffie did call him by Squall in KH1, to which Leon replied: "It's Leon."  Haha, I find it funny that he doesn't like to be called by Squall.

Anything could happen at this point in relation to KH3's plot so maybe yes maybe no