A bit confusing; what I last read:
- Win 9 would be an upgrade for Win 7 enterprise
- Win 10 would be the successor for Win 8, scheduled to ship mid-2015

Where from did you get this information that 'Windows 10 will the last version ever'?

>No, no danger at all. AFAIK Microsoft has declared that WIndows 10 will be their last version ever, after Win10 they will only supply updates from time to time. And since VFP9 works almost perfect on Windows 10, this means that VFP9 also will continue to work "forever". As long as your CPU is Intel or compatible.