If Hayward and Hill both leave(seems like Hill is tied to Hayward, from what he said at exit interviews), I see 3 options really:
1. Retool around Gobert, trying to win as many games as possible - you try to sign players in free agency that will help win right away - Danilo Gallinari, try to trade for Bledsoe using Favors + stuff, opportunistically pluck free agents and other players via trade that will shore up the rotation(Wilson Chandler comes to mind(might have to give up a pick for him), maybe get Lin or Deron or Teodosic as a PG.
2. Rebuild around Gobert - clean everything you can but Gobert for future assets(This would include JJ, Favors, possibly Hood). Give Dante the ball as a PG and tell him it's his team now, let him see what he can do. No stops, no leash, just go berserk, we don't care if he makes a ton of mistakes, we don't care if we lose a ton of games... au contraire - if Dante's PG skills improve while we are losing a ton of games, that's good. Resign Ingles with the idea of selling him for future assets at next trade deadline. Gobert wants bigger offensive role? He want's post ups? Or isos? Maybe the ocasional 3 pointer? Sure... give it to him. Same as with Dante - results don't matter, lets see what he can develop and what he can't, test his limits offensively, especially if it leads to less wins. Try to get the best pick we can. The top of next year's draft seems pretty good. Doncic, Porter Jr... Bamba. Try to get one of the premier ones. If Gobert gets nicked around All-star break... shut him down. Give Bolomboy(or our rookies) the chance to shine. Pick all 4 rookies and give them legit playing time. See what you have in them and if any of them shows surprising developmental spurt or skills.
3. Burn it to the ground (use Gobert to jumpstart the rebuild) - see "Rebuild around Gobert", but in this case in addition to the other moves, trade Gobert for the bank. If Boston for example gives up Fultz + BKN 2018 for Gobert(he's pretty much the perfect missing piece for them, he covers all their weaknesses and makes them strengths - elite rebounding, interior defense, help/weakside defense). Start from zero for the Jazz, but with two high end assets(Fultz + BKN pick) + possibly high Jazz pick in next year's draft).
I honestly have no idea which one I prefer. I think the one that I hate the most is the retool option. I don't think we will be able to retool quickly and well enough to make it worth it. I don't see a retool path that would make us as good as we were this year for the duration of Gobert's contract and in 3 years we will have to start thinking about keeping Gobert, having wasted 3 years of his prime on the tradmill.
In any case, to me Hayward leaving will be devastating for this team. He is not replacable right now, IMO...