Trekking in the mountains during the late pre-monsoon season is very much possible. BBC Treks has just completed an Everest Panorama trek that enjoyed fantastc weather and views. Sure, there is always a chance of cloud spoiling the views but it is unlikely that this will be more than a day or so. Just be prepared to be flexible with your itinerary in case of poor weather which can happen at this time of year. If the views are hard to find there will always be the local culture to keep you entertained.