Does anyone know if Boss are going to do a successor to the GT 100 ?
It's been 4 years since it was released and I can't help thinking that maybe it's getting left behind with all these new DSP fx like AxeFx, Kempler, Amplifire, Helix.

The four other modelers you mentioned are all higher-end than the current GT100 anyway.
It's predictable that BOSS will, at some point, build a newer version that will handle IRs as those other four do. Current trend and all. But it's also likely that Line 6 and the other current competitors at the GT100's price point will do the same.