Per the JPL"
"Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light-years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis which is heading toward the constellation Ophiuchus. In about 40,000 years, Voyager 2 will pass 1.7 light-years (9.7 trillion miles) from the star Ross 248 and in about 296,000 years, it will pass 4.3 light-years (25 trillion miles) from Sirius, the brightest star in the sky . The Voyagers are destined—perhaps eternally—to wander the Milky Way."http://voyager.jpl.nasa.gov/mission/interstellar.html
Putting this into perspective, Voyager 1 is presently about 12 billion miles from the sun, but in 40,000 years it will get within 9.3 trillion miles of another star. That means on its closest approach it will be roughly 800 times farther away from the star it will pass in 40K years than it is from our sun presently.