In reply to rossn:
The area around the Hornli will be closed off for storing materials and providing landing space for helo loads. The best camping will be above The Schwarzee where folk have built stone walls to provide elements of shelter. I think the spot is some 30 minutes below Hornli.
I would recommend contacting the Guides' Bureau as they wil have detailed info. on what's happening; especially as some of the planned work may be to replace some of the fixed ropes which could in effect close the route - a concept not familiar to us here but may well be enforced locally.