The idea is to get everyone to C5 with pregnancy, except Lin of course, who is already completely corrupted and just needs pregnancy. It's hard to argue that I'm more than half way done with the game... although for one year of the games two year development I was making pretty slow progress and I've recently picked that up a LOT.
As for other engines... I would like to delve out into something that I could eventually publish to steam. Not that I'm a money grubber, I just really like being able to eat. At the same time though I have a growing expertise in my current engine as well as various communities being oddly entrenched in the art styles which can make it difficult to change.
Although if you're referring to Renpy and instead moving into unreal or some such... Renpy makes a tremendous amount of development really easy, which lets me concentrate on creating content and that's hard to pass up. If I did change it would be to unreal, I've got a decade of industry experience in it, although it does now give me PTSD.