The answer is yes, GAMA will be needed for the foreseeable future. There are 90+ KingAirs in the fleet that must still be flown. The KingAir goes places that neither the XL or the X, or many other jets for that matter can go legally. The partnership has done 2 things. 1. It has increased the lift availability for WU. 2. It’s allowed Delta to take a step back without totally backing out of the private market. Both brands should thrive.
Now, I’m not going to prognosticate on what will happen down the road, but these partnerships are solid for the time being.