Yes, a 1990 Chevrolet Blazer K5's removable top is very likely to leak after the initial seal has been broken. The seals on these older vehicles are made of rubber and deteriorate over time due to sun exposure, age, and the elements. Once the seal is compromised, even slightly, water will find its way in. The nature of the removable top design means there are many potential points for leaks to develop once the seal is no longer completely effective.
Repairing leaks often involves replacing worn-out seals, applying new sealant, or even replacing damaged sections of the top itself.