John,
I believe there is an old axiom about baseball that says that if a team is .500 at All Star break, anything can happen.
Anyway, if the Twins are a .500 team at All Star, I suspect the Twins become buyers, if they can get a front line pitcher. However, I think the Twins will also weigh short term interests against the long term. I don't think the Twins will give up the farm for a rental arm.
Which takes me to my second thought..I think the Twins are really on the horns of a dilemma. The Twins, as you pointed out in another post, have what appears to be an excellent core of position players that should be enable the team to win over the next few years, if the starting pitching comes around. But, can the Twins afford to give up any of the core players for anything less than a haul of front line prospects? I just don't see it happening for less than several pitching prospects. (Calvin Griffith, if memory serves, always said you never trade position players straight up for a pitcher, because position players are every day players, whereas pitchers pitch once every 5 days)
I think the Twins stand pat this year (Liam Hendricks is waiting in the wings) and let a lot of salary go (Capps, Pavano, Marquis, Liriano) and do something they're not known to do: go after a top of the line free agent starting pitcher.
Of course, I can see the Twins completely blowing up the team if this team doesn't play at least .500 ball this year.