关于使用by
问题描述：
关于使用by
According to some demographers,the number of united states citizens aged 65 or older is likely to rise to 87 million by 2050.
不是出现 by+未来时间就要用将来完成时么?这句话为什么用了一般现在时.不解.
答
is likely to 表达将来