If they do [as I agree they should] get ALC on HW2.x + EAP, the experience is guaranteed to be a qualitatively very different one than ALC on HW3 + FSD, in terms of improved perception accuracy, path fluidity and overall safety, given that the latter will have the cameras running at full resolution and frame rates, on greatly expanded neural nets, whereas the former will remain restricted and on the current nets, due to its processor capacity already being about maxed out [hence resulting in a more error-prone and jerky path].
OTOH those new buyers who await HW3 appearing in series production, then take AP only, should, for the same reasons, get a much more reliable Autosteer and TACC than is available on the current system [minus NoAP, ALC, etc.]
A 30-day FSD-trial will in all likelihood be offered when it is in a decent working order and, if purchased, [the realistic estimate is] around Jan 2023 the nags should be removed to give a true general-purpose L3 AV system.
Hence my recommendation would be to steer towards HW3 by any means necessary, both as a safer and more enjoyable vehicle and a better long-term investment/resale value!
On build-date 22 March 2018, according to my very competent and friendly sales advisor, who steered me to one built in late April.
I don't think they can afford to risk pushing their luck any further on that front.
It is more likely that the relatively small number [perhaps 10,000] of HW2.0 owners who had pre-purchased FSD will have their cars bought back/exchanged if a retrofit of wiring, servos, cameras, etc., up to HW2.5 standards is economically infeasible. Whether this happens before or after a class-action lawsuit is matter for "negotiations" between the affected owners and Tesla, but now would be the perfect time to start organising / agitating to ensure the right thing gets done a.s.a.p.
Cameras and radar are definitely different in HW2.5 from 2.0, also redundant wiring and steering servo were added. Not sure when the ultrasonics were upgraded but suspect they were in 2.0 already.