It's "possible". If you care about performance, then it's not. Obviously I'm not defining "performance", but you'll know this when you see this. Paging is the kiss of death for performance.
Paging has nothing to do with this. When I say 1 MB thread stacks, it means the maximum size of that thread's stack in the virtual address space [0]. Each of these million threads could be using only a few KBs for its stack (out of that 1 MB of stack space). That would imply a few gigs of physical memory => no paging.
[0] http://man7.org/linux/man-pages/man3/pthread_attr_setstacksi...