Keep in mind that Kickstarter is not a pre-order system, and does not make games immune from the normal development process. Sometimes things take longer than expected, and if expectations are off enough it can be much longer.
The Linux version is still coming, it is a native port not a Wine package, and anyone who back the D:OS Kickstarter for the Linux version and found the delay unacceptable could get a refund.
I wasn't involved in deciding the timing of the Kickstarter, but presumably it would benefit both having the D:OS 2 Kickstarter during the lead up to the Enhanced Edition release. PAX Prime is at the end of August, as well.
For the most part it isn't the same set of people working on both games, so there isn't actually a need to wait for one to release before starting a Kickstarter for the other.
