Does a tia always mean a degenerating future?

I don't think so?: I'm guessing that you mean that TIAs signify that strokes will inevitably supervene? And then more, & then more? Not so. Drug therapy, lifestyle changes & in some cases surgery can arrest or reverse the process. Check out the website of the American Stroke Association.

One third of TIA's: are followed by a stroke. One third may re-occur. It depends on a lot of things. (cause, location -anterior circulation vs posterior circulation, treatment (aspirin etc)

What is a TIA: No not at all. By definition, the symptoms of a TIA last 24 hours or less. What is important is that the risk factors for TIA are minimized. These are normally high blood pressure, diabetes, etc. http://www.neurocuro.com/what-causes-a-stroke/

Modify risk factors: A TIA is a warning sign. If you have a surgically correctable problem, great. If you have risk factors like hypertension, obesity, high cholesterol, smoking, then you can do a lot to reduce your risk. If you have plaque build-up in your vessels a 10% fat diet, like Dean Ornish's, can cause plaque regression in five years. So you have a lot of control of the future in this case if you want to.