Along with cpu's ARM also makes mobile gpu ip (Mali), nvidia as well in their tegra. I would be surprised if this deal went through.
Apple built their GPU studio from ex-Imagination staff and will introduce 3 GPUs over the next year: Sicilian, Tonga, Lifuka to support their mobile and desktop plans.
The question is whether ARM will sub license this combined GPU tech, or if it will be NVidia silicon only.