Nah, I think it most certainly means that the kids will arrive in 2012.04.13. Since while Homestuck was going for more than 2 years now, for the kids, it was still the same day. Three years from that is 2012.04.13. So basically Hussie just told us how long Act 6 will probably last. Or at least how long we'll have to wait till the kids arrive in the new session.