Carlson is listed as restricted on the Bakersfield roster; my experience watching this in the past indicates that he'll likely be activated when there's an open spot at an appropriate level. Kaskow was listed as having retired on the Dayton season preview. Carson and Walker both saw a pretty fair number of innings last year (primarily at Low-A) and while they're both 40+-round draft picks, I'd be a tiny bit surprised if they were both gone just like that. Walker, especially, is a 6'5" lefty who has really good control.
Anyway, thanks for adding the minor-league transactions to the thread; I will try to do that on my own each week since I already use those posts to compile the ex-Reds information, etc.