YES, a new jeep track (an unpaved road) has been built connecting Jomsom to Lo Manthang and even further. On any given day, on average, there are around 6 to 8 jeeps, a few trucks and tractors and anywhere from 5 to 15 motorbikes using these jeep tracks. There are a lot more jeeps and trucks (and helicopters) during the Tiji Festival in May/June. So, yes, this does affect the classic trekking route to Upper Mustang. We do understand that no one wants to trek on a trail alongside jeeps, trucks and motorbikes. But there are ways to avoid the jeep track so as to not diminish your trekking experience. A majority of the locals in Mustang are still reliant on tourism and so they along with the Annapurna Conservation Area Project (to whom you pay $30 per person) are trying to build/open an alternative trekking path so you may avoid the jeep tracks. We recently had a trekking group trek this area and below is a report from our guide, Manju Rai, on the alternative route. See below:
Jomsom to Kabgeni: The trail from Jomsom to Kagbeni is all on Jeep track. Although, you could walk part way along the river to avoid the main jeep track.
Kagbeni to Chele: The trail from Kagbeni to Chele too is all along the jeep track. Again, you could avoid some of the jeep track by walking along the river.
Chele to Syangbochen: Walk 3 hours on the jeep track to Samar. You can avoid this jeep track now as the locals are building an alternative trekking route to Samar via Lo Gekar. After Samar, there is an alternative trekking trail which avoids the jeep track which has been built on the previous trekking route. To do this, follow the trail East of the jeep track to Syangbochen via Chungsi caves.
Syangbochen to Dhakmar: Start with a 1 hour hike on the jeep track to Giling – this cannot be avoided. From Giling, instead of taking the jeep track which has now replaced the old trekking trail, follow the alternative trekking trail for 5 hours of hiking to Dhakmar via Karki La pass.
Dhakmar to Lo Manthang: From Dhakmar, hiking is all on trekking trail via Ghar Gompa and Mu la pass. This is a slightly long and strenuous day of about 10.42 miles; 2,536 feet of elevation gain; 2,270 elevation loss.
There are two routes for the return from Lo Manthang to Jomsom. If you have a few extra days and can hike 7 to 8 hours daily, you can take the route East of the Kali Gandaki river trekking via Dri, Tange and Tetang. If not, follow the route below which is basically retracing the same route you used to come up to Lo Manthang.
Lo Manthang to Tsarang: Leave Lo Manthang and follow the road for about 1 hour to Lo La. From here, instead of taking the road back to Tsarang, turn West and descend on the trekking trail to Dhi for about 3 hours. From Dhi, continue 2 hours by road along the river to Tsarang khola and then turn East on the trekking trail for a 1.5 hours trek to Tsarang.
Tsarang to Ghemi – All trekking trail today: 3 hours trekking trail to Dhakmar and 1 hour to Ghemi.
Ghemi to Giling – Another day of all trail hiking: 20 minutes hike to the river and 4 hours trekking trail to Giling.
Giling to Chuksang – The hike back to Syangbochen on the road is unavoidable. Followed by 3 hours of hiking on the trekking trail via Chungsi cake to Samar. 3 hours road hike to Chuksang.
Chussang to Muktinath – Instead of taking the jeep track back to Kagbeni, head east towards Muktinath. Note, this is a more strenuous route with around 2,500 – 3,000 feet of elevation gain taking a total of around 7 hours. Begin by hiking 45 minutes on the road to Tetang followed by 5 to 6 hours of mostly ascent on trekking trail to Muktinath where your trek ends. You can then choose to return to Jomsom by local jeep or you can continue to hike (the next day) on trekking trail down to the Lubra valley and onward to Jomsom.