I do not think Zee5 content will be dropped from airtel platform unless Amazon signs an exclusive deal with them. Zee can very well continue to enter into agreements with multiple players like they r doing right now for grabbing more eyeballs for their content.
As mentioned in article too, there is difference between creating content and having expertise in distributing thru OTT mode. Zee is pioneer in content creation but has limitations in ability to run a OTT platform on larger scale. They need a partner for digital expansion which is why they r looking for an international partner to have sizeable footprint on new age entertainment mediums