Personally, I've never really cared if a dev misses a deadline. They're self imposed anyway. The more important thing to me is that they give some kind of reasonable updates on progress. They don't necessarily even have to have a set deadline. It could be something like "making good progress, no ETA yet" early in a cycle. Later in the cycle it might be something more like "getting close to finishing the next update, ETA 1 week". When running into problems it might be something more like "having unexpected issues, probably going to take an extra week". Something like that would keep me happy even if he never actually sets a deadline in advance. What I don't like is when you get radio silence for 6 months and wonder if he got hit by a bus (I'm talking about devs in general, not Aleksy in particular).
I imagine this next update will be an important one for Aleksy since it will give his supporters a good idea of whether the rebuild is going to pay off with faster development eventually or if it's going to end up being the equivalent of like a year with no content compared to the previous version. So if it was me I would rather release a good update a bit late than a bad one on time.