Paul, it’s hard to say.
I talked with a few trekking agencies in Kathmandu and their advice was to wait and see how the situation evolves over the next week(s). Access to supplies like food, water, and lodging are severely limited in the mountains right now, especially in the Everest and Langtang regions.
The Far West or Mid-West regions didn’t experience any affects from the earthquake, so they should be open for trekking. Getting to these regions and getting a commercial flight into Kathmandu, on the other hand, would be difficult in the immediate future.
I know you’re planning your trek for a month from now, so best thing to do now is monitor the situation and decide from there. We should be getting some updates on trekking in the Everest region in the near future.