Why have not the conscecrandi not been announced yet publicly? Msgr. Lefebvre announced his four candidates far in advance of June 30, 1988.
Maybe they're afraid that the Conciliars would αssαssιnαtҽ them?

I've wondered this myself. There's no GOOD reason for the secrecy.
I suspect that this entire thing is Kayfabe, and that how it plays out has already been mutually agree upon between the SSPX and Rome.
Perhaps they do not want too much prior scrutiny of the "Episcopabili"?
I see a few different ways this might play out.
1) they go ahead and do the consecrations without Rome's approval (at least on the surface, but it's part of the plan), and then Rome declares excommunicate not only the bishops, but perhaps extends it even to priests and the faithful who would attend SSPX chapels (as +Fellay has already hinted)
This would be the outcome of a well-played 5-D chess long game by the diabolical genius of ... Bergoglio (well, it would have to have come from his handler). So Bergoglio gave SSPX jurisdiction for Confessions in 2015. To go along with that, SSPX regularly had Novus Ordo presbyters witness weddings of SSPX faithful. SSPX preached the need for working with Rome, and condemned the Resistance types. As as result of this quasi-regularization, surging attendance during COVID due Conciliar churches shutting down almost completely, and, more recently, by Bergs having shut down most Motu Masses. Those three led to a surge in attendance at SSPX chapels. That surge in attendance, then, appeared to justify the incredibly imprudent massive spending projects by SSPX ... 50 million and counting for the seminary, 25 million and counting for the chapel at St. Mary's ... and a lot of other chapels struggling after having taken on more debt than they could reasonably support.
Now, hanging on with all that debt ... what happens if Rome goes ahead and excommunicates SSPX priests and the faithful who attend their chapels. You'd instantly find SSPX chapel attendance cut by 50%. At that point, they go bankrupt ... belly up, and will be having even the properties they have paid for being seized to pay off their massive debts.
You'd also find a good number of the priests defecting ...
Just speaking with some of the faithful at the SSPX chapel up here, I find that many of them are terrified by the prospect of event he bishops being excommunicated, and are already making escape plans in case that happens. And there's no surprise here, since the SSPX have long used their increasing "regularization" to lure in the Motarian types, which has contributed to a swell in their numbers, but if they lived having swelled their numbers that way, then they'll die by the same means.
If that happens, I would tip my hat and say ... "Well played, Bergoglio. Well played."
2) Just before the consecrations, they'll announce that a deal has been reached, and that they made a compromise with Rome, will only consecrate, say, one or two at most (agreed upon by Rome and undoubtedly either infiltrators or two of the most liberal they can possibly find in their ranks) ... but as part of the deal will extend the ability to perform Confirmations to SSPX priests. That's actually one of the main sticking points, that the two remaining bishops, also getting up there in years, have to travel all over the world doing Confirmations. You don't need 5 bishops just to ordain priests or deacons or sub deacons once each year.
Now, this will have been agree upon from the very beginning ... but was calculated to make it look like the SSPX had NOT "compromised", since the latter had been READY to get excommunicated if necessary. Therefore it will reduce or decrease the suspicion on the new bishops as having been compromise candidates and possible infiltrators.
3) SSPX go ahead with the consecrations, but Prevosts lifts the excommunications, once again showing his "mercy", but the bishops will be, again, agreed upon as being the most liberal that could be found, on a mission to undermine and liberalize the SSPX. This also satisfies both the right wing and left wing within the SSPX, the left due to the mercy and re-regularization, the right because SSPX leadership had shown strenght in standing up to Rome (so it appeared, even though they'd already worked out this Kayfabe), and the left because they're all "regular" again. Then the erosion and weaking of the faith of remaining Traditional Catholics will continue, and possible "full regularization" achieved, so that there will be no difference between SSPX and FSSP, and they gradually fold into the Conciliar Church, perhaps with subtle Liturgical changes (in addition to the theological), so they imperceptibly end up with some "hybrid" liturgy and hybrid Church, via the Hegelian dialectic that Ratzinger favored.