Noms from MOC - depends on the direct competition, who your DS is being compared to in the District.
Senator nom - same, only competition is state-wide.
VP - that’s a huge unknown. I believe the SA chooses for the VP. The SA looks across all the candidates, and there are bound to be ones they are very interested in, across the country, from direct out of HS to college re-applicants to all other sources, who, for whatever reason, did not obtain a nom. That’s just one scenario. The SA has great leeway to use the VP nom as it sees fit, rather like an ace in the hole. It may well be one of the last used, way down the road, in the spring. Or not.
There will be many others in your DS’ position, all application actions complete, apparently solid all-around, even with LOA.
Most regular posters here recommend ensuring the MOC and Senator staffers be provided a copy of the LOA to add to DS’ package. That can be done by your DS in a low-key way, and provides a bit of extra info, that the SA is confident enough to essentially say, we are saving a spot for you if you can get a nom. That also allows those elected officials who use the principal nom method to give that to someone else, since all your DS needs is a nom of any type.
As
@FMHS-79 notes, keep the Plans B and C in play.