MsC, it's really hard when you meet someone you like a lot and feel there's some real potential with, we meet so many men via OD who are just 'meh' that when one comes along who we feel a spark/connection with, you want something to come of it.
I do wonder about him though, do you think he's being honest about having nothing more than a snog for 4 years? I'm not sure if I would believe that, (most) men, especially ones who are on sites all the time, wouldn't have been celibate that long. And if he's not being honest about that, is he lying/playing games about other stuff too?
If he is being honest though (and he may well be of course), the issue still is that he is messing you around a bit, whether deliberately or not. If he's not ready after 4 years, when will he be? It could be a week, a year, another 4 years?...it's really not fair of him to keep you dangling that long. I think I would say to him that you don't want to just be his friend, and unless he is ready to date, there's no point in continuing contact. Now this might galvanise him into action, he might then suggest another date...but then lapse back into the same pattern. Or he might contact you again, but with no promise of a date. Or, he might actually properly get his act together. Worth a try, but I don't think after that I'd give him any more chances tbh.