I'm going to have to disagree with part of this. Collecting emails is a good strategy when there's a concrete availability date and that date isn't too far off from the present. I recently had a client who was trying to sell a similar(ish) product. Collected emails for 6+ months. When they announced that their product was available, it took them 3 months to get to 50 orders from nearly 10k emails. Looking back, keeping the email subs engaged might have helped increase conversion from subscriber -> customer, but It ended up not working out nearly as well as we had hoped.