We shall see. Neptune did not get the Nova job on the strength of being a world-beater in his 5 minutes at Fordham, he got it by virtue of being Jay's guy. Mahoney got the SJU job by the same method.
My observation of assistant coaches who take over well-oiled machines is that you don't know what you have until Year 3 (sometimes Year 4). The first year the muscle memory of the system in place keeps things going on its own unless the assistant is truly awful (which isn't usually the case). In Year 2 there is still enough carryover from the prior regime that it is still hard to differentiate although you start to see some signs. In Year 3 you usually start to have a good idea of whether the guy can do it in his own right.
Historical example of a guy who you found out couldn't was Mahoney. Historical example of a guy who could was Jamie Dixon. Current example of guys who the jury is still out on are Juwan Howard and Neptune. Neptune was not impressive last year but he lost a lot of talent. This year he brought in a lot of talent and is still not impressive thus far (or at least certainly not consistent). It isn't as though you can look at his one season at a bottom-feeder in the A-10 and draw any real conclusions from that. He may turn out to be all that, or he may turn out to be a latter-day Brian Mahoney. My suspicion is more the latter than the former, just not enough sample size yet. But time will tell.
For the opposite lean, see Shaheen Holloway - Year 2, still not enough talent on that roster, but seems very likely to build a winning program.