Jason Castro was the lone Astros' prospect to make the list, coming in at 53rd overall. The estimated arrival date on the big league level for Castro is 2011. From everything I've read that's a pretty conservative estimate. If he were to be our starting catcher in 2010, it wouldn't be all that surprising.
The only thing standing in his way from making a 2010 debut would be the success of JR Towles. Having too many catchers is a problem that any team would like to have. Our prospects are nowhere near this level yet, but we can look at a team like the Texas Rangers as an example of what a luxury having young catchers is. With Taylor Teagarden, Jarrod Saltalamachia, Max Ramirez and Chris Davis all having been catching prospects coming up in the minors, Texas could afford to trade veteran backstop Gerald Laird to Detroit for two pitching prospects. It's a little early to be talking about that kind of scenario applying to the Astros, but it could be an option at some point.