Will support 3dgs not only splat visualization?

### Checklist

- [x] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [x] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [x] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### My Question

I read the recent update about gaussian splat like https://github.com/isl-org/Open3D/pull/7192

But this is only visualization of gaussian splats, not 3dgs, which only containt rgb channel, not the most important alpha blending. Alpha blending need sort, but I didn't see any code about it. I found all the other issues about gaussian splatting are all be closed, so is there any future plan about 3dgs in the future?