Danno (I hope he won't mind me saying) is a perfectionist so doubtless he's recording or re-recording part 4 and it'll be along sometime soon. I was fortunate to subscribe to his song of the month tutorials about 18 months or so ago - I really like Danno's teaching style and I think it's true to say most of what I've learned is down to his teaching and encouragement. His advice on how to organise practice sessions has spilled over in to my work life helping me be more organised there too.
Personally I think it's a shame Danno hasn't continued with his song of the month/week tutorial format, but I suppose it just didn't work out for him commercially - if he was still producing regular wide-ranging tutorials like those at reasonable prices I'd re-subscribe like a shot.