Hud collimation is basically the only thing I regret not having in the F/A-18, and we were preparing for that, but there wasn't enough time to do it in time for the deadline.
There are 3rd party addons products that has been in developement for years (I think it was at least a couple of years since we heard Aerosoft was doing an F16), if we take away the administrative overhead of getting approved, signing contracts, getting the specs and the documentation, out of the total 6 months time that was budgeted, we had only about 3-4 months of real developement time, up to the last week before release, we didn't even had the radar...
So yes, be sure the next airplane we'll do WILL have both collimation and will be conformal (these are two entirely different things, and there's basically no use of a collimated hud, if it's not conformal as well)