[AlexanderTheGr8]

There are huge swaths of interstellar dust (mostly hydrogen) which can be used to slow the probe down.

If not, then we can use a galaxy's resources to slow us down. Basically a complex version of planetary-slingshot.

My argument is, given a century, we are likely to be able to find some way to decelerate. Consider our accomplishments in the last century (airflight, spaceflight, computers, nuclear, internet)