will have done 为什么只能表达猜测意味？
2020年考研英语（一）完形填空中的第一句话是：
Even if families are less likely to sit down to eat together than was once the case, millions of Britons will none the less have partaken this weekend of one of the nations great traditions: the Sunday roast.
疑问：
1）为什么句中will不是将来完成时的助动词，即不是构成will have done - 将来完成时，而只能理解成will情态动词表推测呢？
2）请分析than was once the case语法成分，结构，等含义。
3) none the less, 类似none the wiser, none the worse， 含义和如何使用呢？
如题
