I just did a little math here since I am holding out until the very end days of the event, which we got 17 more quests and 18 days remaining on the clock.
Yesterday, I managed to complete the rush quests so I can get the daily ones. The initials before quest 35 were 1 doubloon each and a daily login of 2 doubloons. As of this moment I have 57 saved up (with no incidents of such showing up for it). The rewards after quest 35 are 2 doubloons each (sitting on after 38 quests are done and waiting on quest 39 to show on reset) and the daily login still has it at 2 doubloons each day.
Anyways, I am estimating (unless the doubloon count will increase after quest 45 is done for the daily reward), that I will have 133 doubloons in total (with a few hours to play the wheel before it ends). If the chance spin/move count is 1 throughout, I would have 133 on the progress bar, and 7 levels of the main building (1 from the surprise box, 2 from the milestone, and 3 from the grand prizes with the level 1 building). If the spin count moves at 2 each, I would have 266 on the progress bar, which would put me 1 less upgrade from max level of the main building. If the spin count moves at 3 each, I would have the full upgraded building and some extra stuff shy of 400 (399).
So, how does Inno guarantee that we will have a full maxed building without spending any diamonds (their announcement)?
Especially, after I saw
@denhviteguden's post above mine on the spin counts. The only way I can think of (remember I don't know if the daily reward will increase after quest 45 which is in a week; might be that famed make sure you done your GE-64 and log in within those hours before it closes kind of quest) is that Inno spews out mostly 2's and 3's on those spins while keeping the 1's to a low number.
However, I won't hold my breath on it because we know how they are when it comes to chance.