I just returned from Mustang. Well the road condition has improved a lot.From Pokhara to Beni, it's almost fully black topped pitched road. From Beni, the off road starts. The road isn't as rough as it used to be. However there were few spots where the roads were muddy near Tatopani and between Tatopani and Ghasa at regular intervals. But I believe the roads have dried by now. When you pass across waterfalls, the roads are muddy. And Since, they have built a bridge at Rupse waterfall, so no more worries about the Rupse landslide. When we were heading towards Tatopani, a river over-flooded and blocked the way few kilometers fromTatopani. It was difficult to cross it as wew were on bike. It was no problem for four wheelers though. When we were back, the water level and its current has decreased. I believe, it should've disappeared by now.
I believe road conditions won't bother you if you're planning to take the trip. if you're planning to go on bike i suggest you to fill your tank at Beni. You can still get petrol at various places but at nrs 150 per litre.