I would bet money against it. More cycling sponsors are leaving the sport than are coming in. Every year there are UCI level teams that are either desperately searching for a new sponsor, folding, or combining with other teams. Which then leaves room for minor sponsors or pro continental teams to step in. You never see headlines that the biggest teams get "bought out" by big sponsors in a bidding war because they are such great investments.

Factor in that Sky's budget is astronomical, they do have a few riders tied up long term, and that they are built with a very niche focus on Grand Tours. Not ever sponsor is going to find that appealing, especially when you consider national interests. Highly unlikely that a major company with strong roots and customer base in Spain, France, Italy, Belgium, or Germany are going to want to back Froome, Thomas, and Bernal as their poster boys.

My guess is that after 2019, Sky will be dismantled as they are today. Another team will step in, and the riders will get picked up. Very similar to what happened to Tinkoff.