2 different contract structures - Seven years/180.0M w/ options and escalators
The second, more likely contract structure, given that the Cubs will have to get creative is a front-loaded deal that carries incentives later in the contract to pay Bellinger more if he still performs well. Consider the first four years to have an AAV of $27MM; the final three years are around $24MM. However, adding a player option after the second season to give him a chance to test free agency in his prime while throwing in a club option for a 5th year gives both parties the option not to get stuck into something long-term.
Of course, guaranteeing only two years of Bellinger when the team wants to compete will be an issue when the time comes. In fact, it will be worse than it is now, given Scott Boras will have more proof that his fantastic client is legit. On the other hand, it at least gives the Cubs a competitive edge for the next two seasons. Still, Bellinger's best two years may be his next two years, and opting out of his own deal can save the Cubs down the road.
The point is that you worry about the future in the future. If you can win now, the team needs to make it happen however they can. This type of deal gets Bellinger paid, whether he does good or bad, and one Hoyer can feel it is not the end of the world for only five years if he underperforms. Any player wants a long-term deal fully guaranteed, but the fact that Bellinger is still a free agent tells you if he were going to receive that, he would have by now. An option-filled deal with escalators is the most likely outcome at this point.