If you followed the road to its conclusion, you'd eventually wind up in Boston. Since this is a one-day trip for me, I generally gas up in the town of Greenfield, Massachusetts, which marks the end of the Mohawk Trail as far as I'm concerned. Now, if you're pressed for time, you can hop on I-91 in Greenfield and head home via the interstates. it won't be pretty, but it'll save a considerable amount of time.
Since I've always got time to ride, my preference is to backtrack down the trail about 12 miles to route 2A..
If you've got any sort of horticultural bent, follow 2A east into the town of Shelburne Falls, a village straight off the set of It's a Wonderful Life. Then follow directions to the Bridge of Flowers. The bridge is an old trolley crossing that was abandoned in 1928. In 1929 the local garden club covered it in flowers and has maintained it ever since. Unique in the world, it's well worth a walk through, even if your interest in gardening starts and ends at the nearest salad bar. If flowers aren't your thing you can check out the local trolley museum or one of the world's largest concentrations of glacial potholes. or if you'd prefer to be a traveler instead of a tourist, just stay in the saddle until you connect with Route 112.
Heading south on 112 presents you with a plateful of optional routes, none of them bad. My favorite is to follow it in a roundabout way toward Route 8, which then points you south into Connecticut. Route 8 is for the most part rural, and very well maintained, and twists through some beautiful forested land. You may be tempted to turn up the wick here, but be careful-the last time I came home this way I plowed through a flock of domestic geese that had decided to see what was on the other side of the road. Hitting one at 75 per will make the ride a lot more interesting than it needs to be.
At the town of Winsted, Connecticut, 8 morphs into a scenic two-lane highway that'll carry you straight to I-84, a major east-west route that'll hustle you toward Hartford, Connecticut, or New York, Pennsylvania and New Jersey. If you'd prefer a more leisurely route, take 44 West into Canaan, Connecticut, and from there you've got access to Route 7 or NY Route 22, which will carry you south in a roundabout way toward the I-84 interchange.
As described here the Mohawk loop runs between 325 and 350 miles, which makes it a perfect one-day wander, and of course an excellent jumping-off point for an extended tour of New England.