if they trade skubal they are most likely going to lose the trade because skubal is already a great player and most prospects - now matter how highly they are ranked - do not pan out.
otoh, there is a very good chance that skubal gets injured again and/or declines from this peak soon (and will still likely outperform any prospect package). only the tigers know their budget. do they want to spend 25% of it on one player?
if you held a gun to my head, i'd say they dont trade him, cant re-sign him, and he walks. but that next year will be very fun when he pitches.