I'm sure this won't happen, VSTEP won't just be creating an entirely new game and forget about Ship Sim 2008. I know this won't happen as VSTEP are NOT like that.
I think the current Ship Sim is a little limited as to the major features it has, and so a complete new rebuild is necessary if they are to incorporate new and exciting features.
However, nothing has been leaked apart from the announcement that the new game is in development, who knows, the two sims may run harmlessly side by side. Don't just speculate until we know a little more.
Ship sim 08 is great, but 09 will probably be twice as good. Anyway, VSTEP will probably have another year to sort out SS08 before the new one is released, so stop panicking about the bugs and stuff guys!!
Look on the brighter side of things!!